I   i 


1 


r 


'.31 


Issued  February  25, 1915. 

AWAII  AGRICULTURAL  EXPERIMENT  STATION, 

J.   M.  WESTGATE,  Agronomist  in  Charge. 


Bulletin   No.  37. 


AMMONIFICATION  AND  NITRIFICATION 
IN  HAWAIIAN  SOILS. 


BY 


W.  P.  KELLEY, 

Chemist. 


U.S..  DEPOSITORY 


UNDER  THE  SUPERVISION  OF 
OFFICE  OF  EXPERIMENT   STATIONS, 

U.  S.  DEPARTMENT  QF  AGRICULTURE. 


WASHINGTON:  *****///** 

GOVERNMENT   PRINTING  OFFICE. 
1915. 


Issued  February  25,  1915. 

HAWAII  AGRICULTURAL  EXPERIMENT  STATION, 

J.   M.  WESTGATE,  Agronomist  in  Charge. 


Bulletin   No.  37. 


AMMONIFICATION  AND  NITRIFICATION 
IN  HAWAIIAN  SOILS. 


BY 


W.  P.  KELLEY, 

Chemist. 


UNDER  THE  SUPERVISION  OF 
OFFICE  OF  EXPERIMENT   STATIONS, 

U.  8.  DEPARTMENT  OF  AGRICULTURE. 


WASHINGTON: 

GOVERNMENT   PRINTING  OFFICE. 

1915. 


HAWAII  AGRICULTURAL  EXPERIMENT  STATION,  HONOLULU. 

[Under  the  supervision  of  A.  C.  True,  Director  of  the  Office  of  Experiment  Stations,  United  States 

Department  of  Agriculture.] 

Walter  H.  Evans,  Chief  of  Division  of  Insular  Stations,  Office  of  Experiment  Stations. 

STATION  STAFF. 

J.  M.  Westgate,  Agronomist  in  Charge. 

J.  Edgar  Higgins,  Horticulturist. 

W.  P.  Kelley,1  Chemist. 

D.  T.  Fullaway,  Entomologist. 

W.  T.  McGeorge,  Chemist. 

Alice  R.  Thompson,  Assistant  Chemist. 

V.  S.  Holt,  Assistant  Horticulturist. 

C.  A.  Sahr,  Assistant  in  Agronomy. 

i  Resigned  October  27, 1914. 
(2) 


LETTER  OF  TRANSMITTAL 


Honolulu,  Hawaii,  January  10,  1914- 
Sir:  I  have  the  honor  to  submit  herewith  and  recommend  for 
publication  as  Bulletin  No.  37  of  the  Hawaii  Agricultural  Experi- 
ment Station,  a  paper  on  Ammonification  and  Nitrification  in  Ha- 
waiian Soils,  prepared  by  Dr.  W.  P.  Kelley,  chemist  of  the  station. 
The  nitrogen  compounds  which  occur  in  soils  and  the  modifications 
which  they  undergo  are  of  great  importance  in  practical  agriculture. 
In  many  Hawaiian  soils  the  conditions  which  influence  the  form  and 
changes  of  these  compounds  are  somewhat  unusual.  A  study  of  the 
factors  which  modify  ammonification  and  nitrification  is  therefore 
of  great  scientific  and  practical  importance.  It  is  believed  that  a 
distinct  contribution  to  the  knowledge  of  these  processes  and  also 
to  an  understanding  of  the  significance  of  the  lime-magnesia  ratio, 
particularly  as  it  is  related  to  changes  in  the  nitrogen  compounds 
of  the  soil,  is  made  in  this  bulletin. 
Respectfully, 

E.  V.  Wilcox, 
Special  Agent  in  Charge. 
Dr.  A.  C.  True, 

Director  Office  of  Experiment  Stations, 

77.  S.  Department  of  Agriculture,  Washington,  D.  0. 

Publication  recommended. 
A.  C.  True,  Director. 

Publication  authorized. 

D.  F.  Houston,  Secretary  of  Agriculture. 

(3) 


CONTENTS. 


Page. 

Introduction 7 

Ammonia  and  nitrate  content  of  uncultivated  soils 9 

Soil  aeration 12 

Ammonification  and  nitrification  in  soils  previously  uncultivated 14 

Effects  of  brief  aeration 14 

Effects  of  lime,  infusions,  and  the  like  on  ammonification  and  nitrification 16 

Effects  of  partial  sterilization 20 

Discussion 32 

The  lime-magnesia  ratio 35 

Effects  of  calcium  and  magnesium  carbonates  on  ammonification 39 

Effects  of  calcium  and  magnesium  carbonates  on  the  ammonification  of  dried 

blood  and  soy-bean  cake  meal 40 

Effects  of  natural  limestones  on  ammonification 42 

Effects  of  calcium  and  magnesium  carbonates  on  nitrification 43 

Nitrification  in  manganiferous  soils 45 

Effects  of  calcareous  and  dolomitic  limestones  on  nitrification 46 

Discussion 46 

Summary 50 

(5) 


AMMONIFICATION  AND  NITRIFICATION  IN 
HAWAIIAN  SOILS. 


INTRODUCTION. 

The  importance  of  bacteria  in  soils  has  become  generally  recognized. 
In  contrast  to  the  extreme  chemical  view  formerly  held  it  is  now  be- 
lieved that  the  biological  activities  going  on  in  soils  are  of  more  funda- 
mental importance,  and  that  as  a  result  of  bacterial  action  the  minerals 
become  more  soluble  and  chemical  transformations  are  brought  about 
in  the  organic  and  inorganic  constituents. 

Soils,  therefore,  are  no  longer  looked  upon  as  dead  reservoirs  of 
plant  food,  but,  on  the  contrary,  as  teeming  with  organized  life. 
Various  chemical  substances,  the  degree  of  porosity,  the  moisture 
content,  and  other  factors,  all  exert  important  influence  on  the  activ- 
ity of  soil  organisms.  For  these  reasons  the  application  of  fertili- 
zers, tillage,  crop  rotation,  etc.,  directly  affect  the  soil  organisms, 
and  therefore,  indirectly,  the  chemical  changes.  But  the  real  seat 
of  bacterial  action  is  the  organic  matter,  and  it  is  this  part  of  the  soil 
that  undergoes  the  greatest  change  as  a  result  of  their  action. 

Practically  all  organic  substances  occurring  in  soils  undergo  decom- 
position to  some  degree  with  the  consequent  formation  of  a  great 
variety  of  chemical  compounds,  principally  organic  in  nature.  Some 
of  these  products  exert  marked  chemical  action  on  the  mineral  con- 
stituents; certain  of  them  are  toxic  both  to  the  higher  plants  and  to 
the  bacteria  themselves,  while  others  serve  as  nutrients  to  the  higher 
plants.  In  the  end,  however,  these  become  converted  into  carbon 
dioxid,  water,  ammonia,  nitrate,  free  nitrogen  gas,  etc. 

Phases  of  soil  bacteriology  which  have  received  a  great  amount  of 
attention  are  ammonification  and  nitrification.  Soil  nitrogen  exists 
principally  in  complex,  insoluble,  protein-like  combinations,  in  which 
form  it  is  unavailable  to  the  higher  plants,  but  by  the  action  of  bac- 
teria ammonia  is  split  off,  which  then  is  oxidized  to  nitrate. 

Formerly,  much  emphasis  was  placed  on  the  numbers  of  organisms 
present  in  soils.  More  recently,  however,  it  has  been  found  that  the 
physiological  efficiency  of  the  organisms  in  different  soils  varies  sc^ 
greatly  that  now  it  is  more  common  to  measure  the  products  of  their 
action  on  nitrogenous  substances  rather  than  to  base  conclusions  on 
the  number  of  organisms  present. 

(7) 


8 

In  considering  the  various  factors  that  influence  the  growth  of 
crops  in  Hawaii,  it  is  inevitable  that  attention  should  be  turned  to 
certain  phases  of  the  nitrogen  question.  In  the  first  place,  Hawaiian 
soils  generally  contain  relatively  large  amounts  of  nitrogen,  on  the 
average  at  least  twice  as  much  as  mainland  soils.  Nevertheless, 
enormous  amounts  of  nitrogenous  fertilizers  are  applied  to  the  land 
now  in  cultivation,  and  in  some  instances  it  has  been  found  very 
profitable  to  use  nitrogenous  fertilizers  on  soils  which  contain  large 
amounts  of  nitrogen.  The  low  availability  of  the  nitrogen  in  the 
soils  emphasizes  the  need  of  a  better  understandirfg  of  the  bacterial 
processes  going  on. 

In  the  second  place,  many  Hawaiian  soils  contain  very  high  per- 
centages of  clay  and  fit  tie  gravel  or  sand,  and,  therefore,  are  very 
close  textured;  consequently  aeration  is  poor.  Such  lands,  espe- 
cially when  plowed  for  the  first  time,  are  exceedingly  inert.  In  the 
pineapple  section  of  Oahu  it  is  necessary  to  allow  the  new  lands  to  lie 
fallow,  with  occasional  cultivation,  for  a  period  of  several  months 
after  the  first  plowing  before  planting,  but  it  has  been  found  that 
the  growth  of  crops  is  normal  and  satisfactory  on  the  new  lands 
immediately  after  plowing,  where  brush  and  other  refuse  had  been 
burned.  Heat,  therefore,  seems  to  accomplish  the  same  effect  as 
continued  aeration. 

In  the  third  place,  Hawaiian  soils  are  extremely  abnormal  in  mineral 
composition.  Various  substances,  such  as  ferric  and  aluminum 
hydrate,  the  oxids  of  manganese,  titanium  compounds,  etc.,  are 
present  in  large  amounts.  Besides,  carbonates,  except  in  a  few 
localities,  are  present  in  extremely  small  amounts.  It  is  commonly 
held  that  the  presence  of  calcium  carbonate  is  essential  to  successful 
crop  production,  for  the  reason  that  nitrification  is  believed  to  be 
dependent  on  it  for  the  maintenance  of  neutral  conditions.  How  far 
other  bases  can  take  the  place  of  calcium  carbonate  is  not  fully  known.1 
The  relative  and  absolute  amounts  of  lime  and  magnesia  in  Hawaiian 
soils  vary  greatly,  but  generally  magnesium  occurs  in  considerably 
larger  amounts  than  calcium.  The  lime-magnesia  ratio  is  a  question 
of  much  interest  among  soil  investigators  at  the  present  time,  but  the 
bearings  of  this  ratio  on  bacterial  action  have  not  been  thoroughly 
studied.  In  view  of  the  large  amounts  of  lime,  some  of  which  is  highly 
magnesian  in  character,  now  being  applied  to  soils,  a  study  of  ammo- 
nification  and  nitrification  as  affected  by  variations  in  this  ratio  is  of 
general  interest. 

In  the  investigation  reported  in  this  bulletin  the  effects  of  certain 
factors  on  nitrification  and  ammonification  have  been  studied,  but 
many  organic  forms  of  nitrogen  are  also  known  to  be  available  to  the 
higher  plants,  and  other  factors  frequently  complicate  the  subject  so 

>  See  Ashby,  Jour.  Agr.  Sci.,  2  (1907),  pp.  52-67. 


as  probably  to  render  the  nitrification  process  of  less  relative  impor- 
tance than  has  been  frequently  assumed.  The  nitrifying  bacteria  ar 
quite  sensitive  to  lack  of  aeration,  the  presence  of  stagnant  water, 
acidity,  certain  chemical  substances,  and  the  like,  but  there  are 
instances  in  Hawaii  in  which  the  intensity  of  nitrification  appears  to 
bear  no  relation  whatever  either  to  the  growth  of  crops  or  to  the 
presence  of  chemical  substances  that  are  definitely  poisonous  to  some 
agricultural  crops.  Hence  the  amount  of  nitrate  and  the  intensity  of 
nitrification  in  a  soil  should  not  be  considered  as  forming  adequate 
measures  of  the  availability  of  nitrogen.  The  results  obtained  in 
nitrification  and  ammonification  experiments,  therefore,  should  be 
interpreted  with  caution,  and  every  known  condition  and  factor,  as 
well  as  the  crops  to  be  grown,  must  be  given  due  weight  before  anything 
like  a  satisfactory  practical  conclusion  can  be  drawn. 

AMMONIA  AND  NITRATE  CONTENT  OF  UNCULTIVATED  SOILS. 

One  of  the  first  questions  studied  in  this  investigation  has  reference 
to  the  rates  at  which  nitrification  and  ammonification  take  place  in 
soils  in  situ.  This  is  obviously  important  in  establishing  a  basis 
for  the  comparison  of  different  treatments  and  as  offering  some 
suggestion  on  the  management  of  these  soils.  It  is  of  special  interest, 
moreover,  for  the  indirect  evidence  furnished  regarding  the  form  of 
nitrogen  that  is  probably  utilized  by  the  different  plants  growing  on 
these  soils. 

While  much  study  has  hitherto  been  devoted  to  nitrification  and 
ammonification  in  cultivated  soils,  so  far  as  the  writer  has  been  able 
to  find  from  literature  at  hand,  very  little  investigation  has  been 
made  on  nitrification  in  sod  lands,  or  soils  lying  long  uncultivated. 
Certain  references  occur  in  the  literature  concerning  the  low  nitrifi- 
cation going  on  in  forest  soils.  Grandeau,1  for  instance,  found  no 
nitrate  in  certain  forest  soils,  while  Weis 2  reported  considerable 
nitrate  in  the  moor  and  forest  soils  of  Denmark.  Ritter  3  found 
little  tendency  toward  nitrate  formation  in  moor  soils,  as  a  rule, 
although  he  detected  small  amounts  of  nitrate  in  certain  cases. 
Petit,4  on  the  other  hand,  found  pronounced  evidence  of  nitrification 
in  a  decidedly  acid  forest  soil  deficient  in  lime.  The  nitrate  content 
of  peaty  soils  in  America,  on  the  other  hand,  is  sometimes  almost 
negligible.  Jodidi5  failed  to  detect  nitrate  in  certain  Michigan 
peats.  It  is  generally  known,  moreover,  that  practically  no  nitrifica- 
tion takes  place  in  the  subsoils  of  humid  climates. 

1  Jour.  Agr.  Prat.,  n.  ser.,  13  (1907),  pp.  645,  646. 
»  Forstl.  Forsogsv.,  2  (1908),  No.  2,  pp.  257-296. 
3  Internat.  Mitt.  Bodenk.,  2  (1912),  No.  5,  pp.  411-428. 
t  Ann.  Sci.  Agron.,  4.  ser.,  2  (1913),  II,  No.  4,  pp.  397,  398. 
■■>  Michigan  Sta.  Tech.  Bill.  4  (1909). 
73729°— 15 2 


19 


In  this  investigation  a  wide  range  of  moisture  and  other  conditions 
were  met  with.  Samples  were  drawn  from  pasture  lands,  submerged 
soils  supporting  a  crop  of  rice  and  taro,  similar  lands  left  to  dry  but 
not  cultivated  after  the  crops  had  been  harvested,  forest  and  fern 
jungles,  abandoned  pineapple  and  cane  fields,  and  the  like.  Some  of 
the  samples  were  drawn  at  times  when  the  soil  was  almost  air  dry, 
while  others  were  taken  when  the  moisture  content  was  near  the 
optimum  for  plant  growth.  The  plants  growing  on  these  soils  repre- 
sent a  considerable  range  of  species. 

When  possible  the  analyses  were  made  immediately  after  taking  the 
samples,  so  as  to  render  unnecessary  the  use  of  antiseptics.  When- 
ever the  sample  could  not  be  analyzed  immediately  a  few  cubic  centi- 
meters of  chloroform  was  added.  Nitrate  was  determined  by  leach- 
ing 100-gram  portions  with  water  and  then  determining  the  nitrate 
dissolved  by  the  use  of  the  phenol  disulphonic  acid  method;  ammonia 
was  determined  by  distilling  100-gram  portions  in  copper  flasks  after 
adding  magnesium  oxid. 

The  results  of  determinations  of  nitrate  and  ammonia  nitrogen  in 
uncultivated  soils  by  these  methods  are  given  in  the  following  table: 

Nitrate  and  ammonia  nitrogen  in  uncultivated  soils. 
[Parts  per  million.] 


Lab. 
No. 

Crop  and  locality. 

Nitrate 
nitrogen. 

Ammonia 
nitrogen. 

229 

Soil 

Pasture,  Wahiawa 

0.2 
.2 
.1 
.1 
.4 
.2 
.4 
.5 

3.0 
Trace. 
.0 
.5 
.7 
.9 

:I 

.1 
.4 
.3 

1.3 

1.3 
.0 

2.5 

.7 

15.0 

5.7 
.5 

2.2 
.4 
.6 
.3 
.3 
.2 
.2 
.3 
.4 
Trace. 

6.0 

1.6 

25.2 

230 

do 

19.6 

233 

Soil     . 

do 

21.0 

234 

do 

11.2 

235 

Soil     . 

do 

16.8 

236 

do 

14.0 

273 

Soil 

Citrus  orchard,  station 

11.2 

292 

do 

Rice,  Waikiki 

2.0 

293 

do 

7.0 

300 
301 

Soil 

Pasture,  Kaneohe 

19.6 

do 

11.2 

302 

Soil  .. 

Abandoned  pineapple  field,  Kaneohe 

19.6 

303 

do 

16.0 

306 

Soil 

Pasture,  Kaneohe 

22.4 

307 
310 

do 

15.4 

Soil 

.:.::So":::: : : : 

16.0 

312 
313 
315 
328 

do 

...do 

21.0 

do 

do 

do 

do 

do 

do 

26.6 

18.2 

Pasture,  Kohala 

12.6 

330 
334 

14.0 

Rice,  Fort  Shatter  .                  

11.2 

335 
336 

.do 

(i) 

337 

Soil 

Rice  land,  Kailua 

(i) 

338 

..do...                      

(i) 

341 

Soil 

C1) 

342 
417 

..do..                      

0) 

Soil 

7.7 

449 

.....do 

do 

do 

do 

do 

14.0 

450 

11.2 

451 

16.8 

452 

26.6 

454 

....do 

42.0 

456 

W.'.Ao.'. 

do 

do 

do 

do 

5.6 

457 

18.2 

458 

30.8 

486 

8 

488 

Not  determined. 


11 

The  very  low  nitrate  content  in  all  the  samples  examined  with  the 
exception  of  Nos.  337,  338,  and  486  will  at  once  be  noted.  Of  these, 
No.  337  was  taken  in  the  Kailna  district  of  Oahu  from  a  rice  field  just 
after  harvest,  and,  being  a  recently  reclaimed  tule  marsh,  the  soil 
contains  a  high  percentage  of  organic  matter  and  is  much  more 
porous  than  the  average  island  soil.  No.  486  was  taken  from  an  old 
pasture  in  the  Kunia  district,  near  the  lands  now  devoted  to  pine- 
apples by  the  Hawaii  Preserving*  Co.  This  soil  is  notably  silty  and 
is  also  much  more  porous  than  the  island  soils  generally.  Therefore 
all  the  uncultivated  soils  examined  which  contained  any  considerable 
amount  of  nitrate  are  porous  and  hence  permit  of  considerable 
aeration  without  cultivation. 

Not  all  the  porous  and  organic  soils  in  the  island  contain  such 
amounts  of  nitrate  when  uncultivated.  Nos.  449  to  458  are  excep- 
tionally well  aerated  soils,  but  none  of  these  contained  more  than 
traces  of  nitrate.  Climatic  factors  in  this  instance  probably  deter- 
mine the  low  nitrate  content.  The  samples  were  taken  from  the 
Hilo  district  of  Hawaii  where  rainy  weather  prevails  a  large  portion 
of  the  year,  but  when  these  soils  are  brought  into  warmer  conditions 
nitrification  has  been  found  to  set  in. 

The  ammonia  content  of  these  soils,  as  shown  in  the  table,  is 
abnormally  high,  ranging  from  2  to  42  parts  per  million.  In  general 
the  ammonia  content  of  soils  elsewhere  is  much  less  than  the  nitrate 
content/  which  is  accounted  for  by  the  fact  that  the  ammonia  is 
nitrified  almost  as  fast  as  it  is  formed.  In  Hawaiian  soils,  however, 
particularly  where  cultivation  is  not  practiced,  nitrification  takes 
place  very  slowly,  in  many  instances  scarcely  at  all,  which,  as  will  be 
shown  subsequently,  is  due  to  the  lack  of  aeration.  Ammonification, 
on  the  other  hand,  not  being  so  dependent  on  aeration  and  also  being 
less  sensitive  to  other  adverse  conditions,  goes  on  more  or  less  uninter- 
ruptedly, with  the  result  that  ammonia  accumulates  to  some  extent. 

As  pointed  out  above,  nitrification  was  formerly  believed  to  be 
necessary  to  the  growth  of  plants.  Experiments  are  not  wanting, 
however,  which  show  that  other  forms  of  nitrogen  can  be  assimilated. 
In  a  number  of  instances  it  has  been  found  that  ammonia  and  organic 
nitrogen  compounds  can  be  utilized  as  advantageously  as  nitrate. 
From  the  experiments  of  Muntz,2  Laurent,3  Griffiths,4  Pitsch,5  Hutch- 
inson and  Miller  6  and  others,  working  under  sterile  conditions,  it  has 
been  shown  that  ammonium  compounds  can  be  assimilated  to  a 

1  Fraps  found  that  some  Texan  soils  also  contain  relatively  large  amounts  of  ammonia.    Texas  Sta.  Bui. 
106  (1908). 

2  Compt.  Rend.  Acad.  Sci.  [Paris],  109  (1889),  p.  646. 
»  Ann.  Inst.  Pasteur,  3  (1889),  p.  362. 

« Chem.  News,  64  (1891),  p.  147. 

6  Landw.  Vers.  Stat.,  34  (1887),  pp.  217-258;  42  (1893),  pp.  1-95. 

«  Jour.  Agr.  Sci.,  3  (1909),  pp.  179-194. 


12 

considerable  extent  by  different  plants.  Moreover,  Kriiger1  found 
that  mustard,  oats,  and  barley  assimilate  ammonia  equally  as  well 
as  nitrate,  while  potatoes  prefer  ammonia.  From  his  experiments 
he  concluded  that  nitrification  is  not  so  necessary  for  cultivated 
plants  as  has  been  supposed. 

In  1910  2  the  writer  showed  that  ammonia  is  greatly  superior  to 
nitrate  in  the  nutrition  of  rice.  It  was  found,  for  instance,  that  rice 
made  very  poor  growth  when  nitrate  was  the  only  source  of  com- 
bined nitrogen  present,  but  different  ammonium  compounds  proved 
well  suited  to  the  plant.  More  recently  Hutchinson  and  Miller3 
have  shown  that  a  considerable  variety  of  organic  nitrogen  com- 
pounds can  be  assimilated  and  transformed  into  protein  by  peas. 
Certain  organic  nitrogen  compounds,  however,  prove  to  be  ill  suited 
to  the  nutrition  of  peas. 

Likewise,  Schreiner  et  al.4  have  demonstrated  that  creatinin  occurs 
in  notable  amounts  in  fertile  soils,  and  is  as  valuable  in  the  nutrition 
of  wheat  as  nitrate. 

From  the  data  above  submitted  it  is  at  once  apparent  that  plants, 
growing  on  the  uncultivated  soils  of  Hawaii,  must  necessarily  depend 
largely  on  forms  of  nitrogen  other  than  nitrate,  for  not  only  is  nitrate 
practically  absent,  but  as  will  be  shown  subsequently,  nitrification 
in  many  instances  will  not  take  place  until  aerated  conditions  have 
been  maintained  for  a  period  of  weeks;  and  the  vigorous  growth  of 
practically  all  the  uncultivated  species  in  the  islands  and  of  such  crops 
as  rice,  taro,  and  bananas,  each  of  which  is  frequently  grown  under 
conditions  which  prevent  nitrification,  furnishes  abundant  evidence 
of  the  availability  of  the  nitrogen  present,  and  points  conclusively  to 
the  dependence  on  forms  other  than  nitrate. 

Since  ammonia  nitrogen  was  found  in  these  soils  in  considerable 
amounts,  and  ammonification  can  take  place  under  the  prevailing 
conditions,  it  seems  justifiable  to  believe  that  ammonia  is  an  impor- 
tant source  of  available  nitrogen  to  the  plants  growing  here,  and  that 
ammonification  is  of  far  greater  importance  than  nitrification. 

SOIL  AERATION. 

The  importance  of  aeration  in  soils  is  generally  recognized.  In 
general,  the  degree  of  aeration  depends  upon  the  porosity  and  water 
content,  and  can  be  greatly  increased  by  tillage.  Notwithstanding 
the  importance  of  oxygen  in  soils,  and  the  fact  that  aeration  stimulates 
bacterial  action,  the  specific  effects  resulting  from  aeration  are  far  from 
being  adequately  understood. 

i  Landw.  Jahrb.,  34  (1905),  p.  761.  3  jour.  Agr.  Sci.,  4  (1912),  pp.  282-302. 

2  Hawaii  Sta.  Bui.  24.  *  U.  S.  Dept.  Agr.,  Bur.  Soils  Bui.  83  (1911). 


13 


In  view  of  the  inactive  state  of  nitrification  in  the  uncultivated  soils 
of  Hawaii,  considerable  interest  is  attached  to  a  study  of  the  effects 
produced  by  aeration.  This  phase  of  the  question  has  been  taken  up 
from  two  slightly  different  standpoints;  first,  with  reference  to  the 
nitrate  and  ammonia  content  of  soils  cultivated  without  any  special 
reference  to  the  time  and  mode  of  tillage,  and  second,  with  reference 
to  the  possibility  of  the  uncultivated  soils  containing  agents  that 
hinder  nitrification. 

The  results  of  the  determinations  of  nitrate  and  ammonia  nitrogen 
in  different  cultivated  soils  are  given  in  the  following  table: 

Nitrate  and  ammonia  nitrogen  in  cultivated  soils. 
[Parts  per  million.] 


Lab. 
No. 


Crop  and  locality. 


Nitrate 
nitrogen. 


Ammonia 
nitrogen. 


274 
288 
289 
290 
291 
304 
305 
308 
317 
319 
326 
327 
329 
331 
332 
333 
339 
340 
416 
428 
455 
459 
485 
487 


Soil.... 
....do.. 
....do.. 
....do.. 
Subsoil. 
SoU.... 
Subsoil. 
Soil.... 
....do.. 
....do.. 
....do.. 

do.. 

do.. 

do.. 

do.. 

Subsoil. 
SoU.... 
Subsoil. 
SoU.... 
....do.. 
....do. 

do. 

do. 

do. 


Citrus  orchard,  station. 

Corn,  station 

— do 

Citrus  orchard,  station . 

....do 

Pineapple,  Kaneohe. . . 

do 

....do 

No  crop,  Kaneohe 

do 

Corn,  Kohala 

Pineapple,  Kohala 

No  crop,  Waipio 

No  crop,  Helemano 

No  crop,  Fort  Shatter. 

do 

No  crop,  KaUua 

do 

Pineapples,  Wahiawa. 

Corn,  Glenwood 

LUies,  Glenwood 

No  crop,  Glenwood 

Pineapples,  Kunia 

Pineapples  Wahiawa. . 


10.0 

4.7 

1.8 

14.5 

6.5 

10.0 

12.6 

17.0 

15.4 

9.7 

19.0 

10.0 

75.0 

32.0 

3.0 

1.5 

10.0 

5.0 

40.0 

7.2 

4.7 

1.0 

10.0 

10.8 


11.2 
16.8 
12.6 
15.4 
16.0 
12.6 
21.0 
19.6 
12.6 
18.2 
15.4 
12.6 
33.6 
28.0 
8.4 
8.4 


11.9 

64.0 
21.0 
4.2 


i  Not  determined. 

A  comparison  of  the  above  data  with  "that  in  the  previous  table 
indicates  that,  when  aerated  conditions  are  brought  about  in  Hawaiian 
soils,  nitrification  generally  becomes  active.  Ammonification  was 
also  stimulated  by  tillage.  However,  as  previously  stated,  nitrifica- 
tion is  at  a  low  ebb  in  certain  soils,  although  well  aerated.  The  above 
table  shows  that  soil  No.  459  contained  only  one  part  of  nitrate  per 
million.  This  soil  had  been  thoroughly  tilled  for  several  months  and 
contained  a  large  amount  of  organic  matter.  The  low  nitrification 
taking  place  here  appears  to  be  due  to  climatic  factors  rather  than  the 
absence  of  the  nitrifying  organisms  and  is  being  further  investigated. 

The  composition  of  the  mineral  matters  in  the  above  soils  varies 
enormously.  No.  329  is  highly  manganif erous ;  No.  485  contains 
about  20  per  cent  titanic  oxid;  No.  288  contains  a  large  excess  of 
magnesia,  while  a  majority  of  these  soils  are  highly  ferruginous,  con- 
taining on  the  average  about  20  per  cent  ferric  oxid.     Since  the 


14 

nitrate  content  bears  no  definite  relation  to  the  amount  of  the  above- 
named  mineral  constituents,  and  in  a  number  of  instances  was  equal 
to  that  found  in  soils  elsewhere,  it  is  safe  to  conclude  that  the  abnor- 
mal mineral  composition  of  Hawaiian  soils  does  not  prevent  active 
nitrification  and  ammonification.  The  temperature  being  near  the 
optimum  for  bacterial  action  greatly  encourages  nitrification  when  the 
other  conditions  are  suitable. 

AMMONIFICATION    AND    NITRIFICATION    IN    SOILS    PREVIOUSLY 

UNCULTIVATED. 

The  inert  character  of  the  virgin  soils  of  Hawaii  has  already  been 
referred  to.  Moreover,  heavy  applications  of  various  fertilizers,  in- 
cluding nitrate,  often  fail  to  induce  vigorous  growth  of  pineapples  on 
the  new  lands.  In  investigating  this  phenomenon,  various  treatments 
have  been  applied,  including  aeration  for  different  lengths  of  time, 
the  application  of  lime,  burning,  and  partial  sterilization.  Large 
samples  of  soil  were  taken  from  uncultivated  fields,  and  at  the  same 
time  samples  of  corresponding  soil  cultivated  at  intervals  for  10 
months  without  having  any  crop  growing  thereon.  At  the  time  of 
sampling  the  nitrate  and  ammonia  were  as  follows: 

Nitrate  and  ammonia  nitrogen  in  cultivated  and  uncultivated  soils. 
[Parts  per  million.] 


Lab. 
No. 

Condition. 

Nitrate 
nitrogen. 

Ammo- 
nia 
nitrogen. 

Lab. 
No. 

Condition. 

Nitrate 
nitrogen. 

Ammo- 
nia 
nitrogen. 

329 

Cultivated 

75.0 
1.3 

40.0 

33.6 
14.0 
11.9 

417 
487 
488 

Uncultivated 

0.4 
10.8 
1.6 

7.7 

330 

Uncultivated 

Cultivated 

C1) 
C1) 

416 

Cultivated 

Uncultivated 

Not  determined. 


The  above  data  again  show  that  aeration  greatly  stimulates  both 
nitrification  and  ammonification,  and  that  the  uncultivated  soils 
contain  an  extremely  low  nitrate  content. 


EFFECTS   OF  BRIEF   AERATION. 

« 
Further  investigation  of  the  effects  produced  by  aeration  led  to  a 

study  of  nitrification  and  ammonification  at  various  intervals  after 

the  samples  were  drawn.     The  samples  were  divided  into  different 

portions.     One  of  each  was  spread  out  in  the  laboratory  to  dry. 

The  nitrate  and  ammonia  were  determined  in  these  portions  at 

intervals,  as  shown  in  the  table  following. 


15 

Effects  of  aeration  on  the  content  of  nitrates  and  ammonia  nitrogen  in  soils. 

[Parts  per  million.] 


Lab. 
No. 

Condition  when 
brought  to  labora- 
tory. 

Days 
after 
bring- 
ing to 
labora- 
tory. 

Ni- 
trate 
nitro- 
gen. 

Am- 
monia 
nitro- 
gen. 

Lab. 
No. 

Condition  when 
brought  to  labora- 
tory. 

Days 
after 
bring- 
ing to 
labora- 
tory. 

Ni- 
trate 
nitro- 
gen. 

Am- 
monia 
nitro- 
gen. 

329 
329 

Cultivated 

do 

None. 

28 
None. 

28 
None. 

14 

315 

None. 

14 

75.0 

160.0 

1.3 

85.0 

40.0 

57.5 

62.0 

.4 

.6 

33.6 
56.0 
14.0 
30.8 
11.9 
12.5 
44.8 
7.7 
12.2 

417 

485 
485 
486 
486 
487 
487 
488 
488 

Uncultivated 

Cultivated 

....do 

315 
None. 

232 
None. 

232 
None. 

200 
None. 

200 

0.5 

10.0 

11.0 

6.0 

5.0 

10.8 

9.0 

1.6 

1.2 

50.4 

0) 
36.4 

330 

Uncultivated 

....do 

330 

Uncultivated 

do 

Cultivated 

do 

0) 

416 
416 

Cultivated 

do 

40.6 
0) 

416 

..do 

61.6 

417 

417 

Uncultivated 

...do 

Uncultivated 

do 

0) 
58.6 

>Not  determined. 

During  the  drying  out,  ammonification  took  place  to  a  considerable 
extent  but  at  a  more  vigorous  rate  in  the  cultivated  than  in  the 
uncultivated  soils.  Nitrification  also  took  place  in  the  cultivated 
soils,  but  with  the  exception  of  No.  330,  was  inactive  in  the  uncul- 
tivated soils.  The  moisture  content  of  these  soils  at  the  time  of 
sampling  was  about  one-half  saturation,  but,  of  course,  rapidly 
decreased.  Nevertheless,  considerable  nitrification  took  place  in 
soils  Nos.  329,  330,  and  416  during  the  first  three  weeks. 

The  portions  to  be  used  in  studying  the  effects  produced  by  aeration 
for  a  brief  time  were  thoroughly  mixed  upon  reaching  the  laboratory, 
placed  in  large  fruit  jars,  sterile  water  added  in  sufficient  amounts  to 
bring  the  moisture  content  to  two-thirds  saturation,  then  loosely  cov- 
ered with  cotton  plugs,  and  kept  at  from  27°  to  30°  C.  in  a  dark  closet. 
At  various  intervals  portions  were  withdrawn  with  a  sterile  spatula, 
and  the  nitrate  and  ammonia  determined.     The  results  follow: 

Ammonification  and  nitrification  in  soils  after  short  periods  of  aeration. 
[Parts  per  million.] 


Lab. 

No. 

Previous  condition. 

Days 
after  tak- 
ing from 

field. 

Nitrate 
nitrogen. 

Ammonia 
nitrogen. 

Gain(+) 

3rloss(— ). 

Nitrate 
nitrogen. 

Ammonia 
nitrogen. 

329 

Cultivated 

None. 
14 
32 
46 

None. 
14 
32 
46 

None. 
14 
28 
42 

None. 
14 
28 
42 

None. 
14 
28 
42 
101 

None. 
14 
28 
42 
101 

75.0 

140.0 

220.0 

220.0 

1.3 

13.0 

14.6 

7.0 

40.0 

70.0 

92.0 

90.0 

.4 

.6 

13.0 

12.0 

10.0 

18.0 

27.5 

31.5 

56.0 

6.0 

18.0 

25.0 

34.5 

70.0 

33.6 
42.0 
22.4 
33.6 
14.0 
11.2 
11.2 
28.0 
11.9 
19.6 
14.0 
28.0 
7.7 
22.4 
42.0 
42.0 
0) 
11.4 
18.2 
7.0 
5.6 
0) 

7.5 
12.6 
14.0 
16.8 

329 

do 

+  65.0 
+  145.0 
+  145.0 

+     84 

329 

do 

—  11  2 

329 

do 

.0 

330 

Uncultivated 

330 

do 

+  11.7 
+  13.3 
+    5.7 

—    2.8 

330 

do 

—     2.8 

330 

....do 

+  14.0 

416 

Cultivated 

416 

do 

+  30.0 
+  52.0 
+  50.0 

+     7.7 

416 

do 

+    2.1 

416 

do 

+  16.1 

417 

Uncultivated 

417 

do 

+      .2 
+  12.6 
+  11.6 

+  14.7 

417 

do 

+  34.3 

417 

do 

+  34.3 

485 

Cultivated 

485 

do 

+    8.0 
+  17.5 
+  21.5 
+  46.0 

485 

do 

2  +    6.8 

485 

do 

J—    4.4 

485 

do 

2  —    5.8 

486 

Uncultivated 

486 

do 

+  12.0 
+  19.0 
+  28.5 
+  64.0 

486 

do 

*  +    5.1 

486 

....do 

2  +    6.5 

486 

do 

2  +    9.3 

1  Not  determined. 


2  Gain  or  loss  after  14  days. 


16 

From  the  above  table  it  will  be  seen  that  nitrification  and  ammoni- 
fication  were  stimulated  by  the  brief  aeration  and  that  a  maximum 
nitrate  and  ammonia  content  was  reached  in  about  four  weeks,  except 
in  the  case  of  soils  Nos.  485  and  486.  It  is  of  special  interest  that  the 
intensity  of  both  nitrification  and  ammonification  in  the  uncultivated 
soils  was  considerably  less  in  every  instance  except  No.  486  than  in 
the  corresponding  cultivated  soil,  which  again  points  to  the  fact  that 
tillage,  for  a  short  time  only,  is  not  sufficient  to  cause  vigorous  bacte- 
rial action.  Soil  486  at  first  appears  to  be  an  exception,  but  it  should 
be  remembered  that  aerated  conditions  ensue  in  this  soil  without 
cultivation.  The  data  obtained  from  it,  therefore,  the  more  strongly 
emphasizes  the  fact  that  aeration  not  only  supplies  the  oxygen  neces- 
sary to  bacterial  action,  but  also  brings  about  other  changes,  directly 
or  indirectly,  which  appear  to  be  fundamental  to  vigorous  bacterial 
action. 

EFFECTS   OF   LIME,   INFUSIONS,    AND   THE    LIKE,   ON   AMMONIFI- 
CATION  AND   NITRIFICATION. 

There  is  a  popular  belief  in  Hawaii  that  the  sod  lands  are  acid,  due 
to  anaerobic  fermentation,  and  that  the  acidity  can  be  overcome 
(neutralized)  by  bringing  about  aerated  conditions  for  a  sufficient 
length  of  time.  Thus  it  is  that  the  farmer  explains  the  beneficial 
effects  of  tillage.  On  the  other  hand,  bacteriologists  hold  that  bac- 
terio toxins  may  accumulate  in  soils  in  certain  conditions,  and  that 
the  nitrifying  organisms  either  may  not  be  present  in  soils  long  re- 
maining under  anaerobic  conditions,  or  lose  in  part  their  physiological 
activity.  In  order  to  throw  some  light  on  these  questions  infusions 
from  a  soil  containing  vigorous  nitrifying  and  ammonifying  floras 
were  added  to  portions  of  the  cultivated  and  uncultivated  soils,  and 
in  addition,  dried  blood  at  the  rate  of  2  grams  and  calcium  carbonate 
at  the  rate  of  1  gram  per  100  grams  of  soil.  After  bringing  to  opti- 
mum moisture  with  sterile  water,  the  soils  were  kept  in  tumblers  at 
temperatures  from  27°  to  30°  C.  for  7  days  in  the  ammonification  ex- 
periments, and  21  days  in  the  nitrification  experiments.  At  the  end 
of  these  periods  the  ammonia  and  nitrate  were  determined,  as  shown 
in  the  table  following. 


17 


Ammonification  and  nitrification  in  cultivated  and  uncultivated  soils. 
[Parts  per  million.] 


Lab. 
No. 


Previous  Condi- 
tion. 


Treatment. 


Ammonia 

Nitrate 

nitrogen 

nitrogen 

found. 

found. 

37.8 

135.0 

40.6 

143.0 

1,519.0 

131.0 

1,503.0 

129.0 

1,532.0 

132.0 

11.9 

22.4 

12.6 

20.8 

925.0 

9.9 

1,219.0 

9.5 

1, 144. 0 

11.0 

10.5 

78.0 

6.3 

82.0 

1,486.0 

186.0 

1,472.0 

178.0 

5.9 

2.5 

5.6 

4.2 

1,034.0 

3.5 

1,130.0 

2.2 

Cain  (  +  )  or  loss  (— ). 


Ammonia 
nitrogen. 


Nitrate 
nitrogen. 


329 
329 
329 
329 
329 

330 
330 
330 
330 
330 

416 
416 
416 
416 
417 
417 
417 
417 


Cultivated. . . 

do 

do 

do 

do 

Uncultivated 

do 

do 

do 

do 

Cultivated. . . 

do 

do 

do 

Uncultivated. 

do 

do 

do 


None 

Infusion 

2  gm.  dried  blood 

2  gm.  dried  blood+1  gm.  CaC03 

2  gm.  dried  blood+1  gm.  CaC03+ 

infusion. 

None 

Infusion 

2  gm.  dried  blood 

2  gm.  dried  blood+1  gm.  CaC03 

1  2  gm.  dried  blood+1  gm.  CaC03+ 

infusion. 
None 

1  gm.  CaC03 

2  gm.  dried  blood 

2  gm.  dried  blood+1  gm.  CaC03 

None 

1  gm.  CaC03 

2  gm.  dried  blood 

2  gm.  dried  blood+1  gm.  CaC03 


+  4.2 
+  7.0 
+1,485.4 
+  1,469.4 
+1,498.4 

-  2.1 

-  1.4 
+  911.0 
+1,205  0 
+  1,130.0 

-  1.4 

-  5.6 
+1,474.1 
+1,460.1 

-  1.8 

-  2.1 
+1,026.3 
+1,122.3 


+  600 
+  68.0 
+  56.0 
+  54.0 
+  57.0 

+  21.1 

+  19.5 

+  8.5 

+  8.2 

+  9-7 

+  38.0 
+  42.0 
+146.0 
+  138-0 
+  2.1 
+  3.8 
+  3.1 
+    1.8 


The  above  results  show  that  previous  cultivation  produced  remark- 
able effects  on  ammonification  and  nitrification,  especially  the  latter. 
Thus  it  was  found  that  the  nitrates  in  cultivated  soils  Nos.  329  and 
416  without  treatment  increased  in  21  days  from  75  and  40  parts 
to  135  and  78  parts  per  million,  respectively,  while  the  nitrate  in  the 
corresponding  uncultivated  soils  Nos.  330  and  417  increased  from  1.3 
and  0.4  parts  to  only  22.4  and  2.5  parts,  respectively.  Expressing 
these  results  in  another  way,  cultivated  soil  No.  329  gained  60  parts 
per  million  of  nitrate  nitrogen,  while  the  corresponding  uncultivated 
soil  No.  330  gained  only  21.1  parts,  and  cultivated  soil  No.  416 
gained  38  parts  per  million,  while  the  uncultivated  soil  No.  417 
gained  only  2.1  parts. 

The  addition  of  active  infusions  brought  about  only  slight  increase 
in  nitrification,  while  the  addition  of  dried  blood  caused  a  slight 
decrease  in  nitrates  in  soil  No.  329,  and  a  considerably  larger  decrease 
in  soil  No.  330.  On  the  other  hand,  nitrification  in  soil  No.  416 
was  greatly  stimulated  by  the  addition  of  dried  blood,  but  no  effects 
were  noticed  in  the  corresponding  uncultivated  soil  No.  417.  Only 
slight  effects  were  produced  by  the  addition  of  calcium  carbonate, 
thus  showing  that  acidity  is  not  the  cause  of  the  low  nitrification  in 
these  soils. 

Turning  to  the  effects  produced  on  ammonification,  we  find  that 
neither  the  addition  of  active  infusions  nor  of  lime  produced  any 
effects,  but  that  the  ammonification  of  dried  blood  was  active  in 
every  case,  although  proceeding  with  more  vigor  in  the  cultivated 
soils. 


73729° 


18 


As  further  showing  that  something  more  than  the  mere  supplying 
of  free  oxygen  and  active  infusions  is  necessary  in  order  to  bring 
about  nitrification  in  these  soils,  the  experiments  reported  in  the 
following  table  were  carried  out  with  soils  Nos.  487  and  488.  Soil 
No.  487  came  from  a  field  which  had  been  thoroughly  cultivated  for  a 
period  of  months,  but  for  three  weeks  immediately  previous  to 
sampling  excessively  wet  weather  had  prevailed,  during  which  time 
the  soil  had  been  saturated  practically  all  the  time.  Soil  No.  488 
represents  the  corresponding  uncultivated  soil. 

Ammonification  and  nitrification  in  soils  after  continuous  rains. 
[Parts  per  million.] 


Lab. 
No. 


Previous  condi- 
tion. 


Treatment. 


Nitrate 
nitrogen 
found. 


Ammonia 
nitrogen 
found. 


Gain  (  +  )  or  loss  (—). 


Nitrate 
nitrogen. 


Ammonia 
nitrogen. 


487 
487 
487 
487 

488 
488 
488 


Cultivated. . . 

....do 

....do 

....do 

Uncultivated 

....do 

....do 

....do 


None 

2  gm.  dried  blood 

2  gm.  dried  blood+2  gm.  CaC03 

2  gm.   dried  blood+2   gm.   CaC03+ 

infusion. 

None 

2  gm.  dried  blood 

2  gm.  dried  blood+2  gm.  CaC03 

2   gm.    dried   blood+2   gm.    CaC03+ 

infusion. 


13.2 
7.7 
13.5 
11.5 

2.7 
2.6 
7.2 
5.5 


53.0 
281.0 
239.0 
235.0 

60.2 
303.1 
227.5 
226.1 


+2.4 
-3.1 
+2.7 
+0.7 

+1.1 
+  1.0 
+5.6 
+3.9 


0.0 

+228.0 
+186.0 
+182.0 

0.0 
+242.9 
+  167.3 
+  165.9 


Here  we  see  that  ammonification  took  place,  although  not  so 
actively  as  in  the  soils  previously  discussed,  and  that  neither  lime  nor 
active  infusions  brought  about  any  increase  over  that  which  occurred 
without  them.  Practically  no  nitrification  took  place  in  any  portion 
of  the  cultivated  or  uncultivated  soil.  Thus  while  the  previous  culti- 
vation had  affected  the  nitrate  content  to  a  slight  extent,  the  beneficial 
effects  produced  were  very  soon  destroyed  in  the  saturated  condition. 
These  soils  contain  a  very  high  clay  content  and  a  small  amount  of 
humus,  and  the  clay  is  exceedingly  deflocculated.  Continued  rains, 
therefore,  cause  packing  and  bring  about  anaerobic  conditions. 

In  the  following  series  10  cubic  centimeters  of  infusion,  obtained  by 
vigorously  shaking'for  10  minutes  100  grams  of  uncultivated  soil  No. 
417  with  200  cubic  centimeters  sterile  water,  were  added  to  100  grams 
of  the  cultivated  soil  No.  416  both  with  and  without  dried  blood  and 
calcium  carbonate.  At  the  same  time  infusions  from  the  cultivated 
soil  were  added  to  portions  of  the  uncultivated  soil.  After  the  usual 
incubation  periods,  ammonia  and  nitrate  were  determined,  with  the 
results  shown  in  the  table  following. 


19 


Ammonification  and  nitrification  as  affected  by  infusion  from  the  cultivated  and 

uncultivated  soils. 

[Parts  per  million.] 


Lab. 
No. 

Previous  con- 
dition. 

Treatment. 

Ammonia 
nitrogen 
found. 

Nitrate 

nitrogen 

found. 

Gain  (  +  )  or  loss  (—). 

Ammonia 
nitrogen 

Nitrate 
nitrogen. 

416 

Cultivated 

do 

do 

do 

Uncultivated  . 

do 

do 

do 

10.5 

8.4 

1,472.0 

1,437.0 

5.9 

78 

79 
178 
157 

2.5 
3.8 
2.2 
10.1 

-  1.4 
3.5 

+  1,460.1 
+  1,425.1 

1.8 

-  2.1 
+  1,122.3 
+  1,094.3 

+  38.0 

416 

Infusion  from  No.  417 

+  39.0 

416 
416 

417 

2  gm.  dried  blood+1  gm.  CaC03 

2  gm.  dried  blood+1  gm.  CaC03+infu- 

sion  from  No.  417. 
None 

+  138.0 
+  117.0 

+     2.1 

417 
417 
417 

Infusion  from  No.  416 

2  gm.  dried  blood+1  gm.  CaC03 

2  gm.  dried  blood+1  gm.  CaC03+ infu- 
sion from  No.  416. 

5.6 
1,130.0 
1, 102. 0 

+     3.4 
+     1.8 
+     9.7 

Practically  no  effects  were  produced  by  adding  infusions  from  the 
cultivated  to  the  uncultivated  soils,  or  vice  versa,  except  where  dried 
blood  and  lime  were  added  also.  In  these  instances  the  infusions 
from  the  uncultivated  soil  caused  a  decrease  in  both  nitrification  and 
ammonification,  whereas  adding  infusions  from  the  cultivated  soil 
caused  a  stimulation  in  nitrification.  The  inhibiting  agent  in  the 
uncultivated  soil,  therefore,  seems  to  be  capable  of  being  transferred 
in  a  water  solution,  although  the  results  are  not  entirely  convincing. 

In  order  to  study  the  effects  brought  about  by  sterilization,  100- 
gram  portions  were  heated  in  an  autoclave  for  two  hours  at  a  pressure 
of  two  atmospheres.  After  cooling,  dried  blood,  calcium  carbonate, 
and  infusions  from  the  original  soils  were  added,  optimum  moisture 
conditions  brought  about,  and  incubated  for  the  usual  periods.  The 
ammonia  and  nitrate  that  accumulated  are  shown  in  the  following 
table: 

Ammonification  and  nitrification  after  sterilizing  in  autoclave. 
[Parts  per  million.] 


Lab. 
No. 

Previous 
condition. 

Treatment. 

Ammonia 
nitrogen 
found. 

Nitrate 

nitrogen 

found. 

416 

Cultivated 

do 

No  inoculation 

12.5 
18.0 
35.0 
37.1 
17.2 
31.5 
32.1 
12.2 
19.0 
35.2 
37.4 
18.9 
31.5 
SI.  6 

57  5 

416 

Infusion  from  No  416 

51.0 

416 

do 

Infusion  fromNo.  416+2  gm.  dried  blood 

51.0 

416 

.do 

Infusion  from  No.  416+2  gm.  dried  blood+1  gm.  CaC03 

Infusion  from  No.  417 

55  5 

416 

....do 

52.0 

416 

....do 

Infusion  from  No.  417+2  gm.  dried  blood 

51.0 

416 
417 

do 

Uncultivated., 
.do 

Infusion  from  No.  417+2  gm.  dried  blood  +  1  gm.  CaC03 

No  inoculation 

51.0 
.6 

417 

g 

417 

do 

do 

do 

do 

do 

Infusion  from  No.  416+2  gm  dried  blood 

.8 

417 
417 

Infusion  from  No.  416+2  gm.  dried  blood  +  1  gm.  CaC03 

Infusion  from  No.  417 

1.2 
.4 

417 

Infusion  from  No.  417+2  gm.  dried  blood 

1.4 

417 

Infusion  from  No.  417+2  gm.  dried  blood+1  gm.  CaC03 

1.9 

These  data  show  that  the  ammonifying  organisms  occurring  in  the 
cultivated  and  uncultivated  soils  are  equally  active,  and  that  ammon- 


20 

ification  took  place  in  the  two  soils  at  practically  the  same  rates 
after  sterilization.  On  the  other  hand,  no  nitrification  took  place  in 
the  previously  cultivated  soil,  and  only  to  a  very  slight  extent  in 
that  uncultivated.  Ammonification  took  place  much  less  vigorously 
in  these  soils  after  having  been  sterilized  than  before,  although  it 
should  be  remembered  that  in  the  initial  stages  of  the  ammonification 
a  much  smaller  number  of  organisms  was  present  than  originally 
occurred  in  the  soil.  It  is  probable,  however,  in  view  of  the  absence 
of  nitrification,  and  the  fact  that  toxic  conditions  are  known  to  be 
brought  about  by  steam  heat,  that  conditions  somewhat  toxic  to 
ammonification  were  developed.  The  point  of  greatest  interest  in 
these  results  is  that  by  sterilization  in  the  autoclave  changes  were 
brought  about  in  the  cultivated  and  uncultivated  soils,  so  that  am- 
monification proceeded  subsequently  at  practically  the  same  rates 
in  each. 

In  order  to  study  the  effects  of  still  higher  heating,  portions  of 
cultivated  and  uncultivated  soils  Nos.  329  and  330  were  heated  in 
porcelain  dishes  over  the  free  flame  of  a  Bunsen  burner  for  a  period 
of  10  hours.  After  cooling,  each  was  treated  with  dried  blood,  calcium 
carbonate,  and  an  active  infusion.  At  the  end  of  the  usual  incubation 
periods  the  ammonia  and  nitrate  were  determined,  with  the  following 

results : 

Ammonification  and  nitrification  after  burning. 

[Parts  per  million.] 


Lab. 
No. 


Previous 
condition. 


Treatment. 


Ammonia 
nitrogen 


Nitrate 
nitrogen. 


329 
329 
329 
330 
330 
330 


Cultivated . . . 

....do 

....do 

Uncultivated 

....do 

....do 


Immediately  alter  burning 

Active  infusion 

2  gm.  dried  blood+1  gm.  CaC03+ active  infusion 

Immediately  after  burning 

Active  infusion 

2  gm.  dried  blood+1  gm.  CaC03+active  infusion 


274.0 
254.0 
899.0 
183.0 
206.0 
929.0 


26.0 
30.0 
32.4 
18.8 
13.0 
17.1 


In  the  first  place  heat  caused  an  initial  splitting  off  of  a  large 
amount  of  ammonia  and  a  partial  decomposition  of  the  nitrate.1 
The  subsequent  ammonification  was  practically  the  same  in  each 
soil,  however,  while  nitrification  took  place  to  a  slight  extent  in  soil 
No.  329  only.  Thus,  again,  it  is  shown  that  heat  reacts  on  the  cul- 
tivated and  uncultivated  soils  of  Hawaii  in  such  way  as  to  bring 
them  into  similar  conditions  so  far  as  bacterial  action  is  concerned. 

EFFECTS   OF   PARTIAL    STERILIZATION. 

For  a  number  of  years  it  has  been  known  that  plant  stimulation 
may  be  brought  about  in  soils  by  means  of  heating  and  by  the  appli- 
cation of  such  substances  as  carbon  bisulphid,  chloroform,  etc.     The 


Hawaii  Sta.  Bui.  30  (1913). 


21 

effects  produced  thereby  are  now  commonly  considered  to  be  due  to 
effects  produced  on  the  soil  organisms  either  directly  or  indirectly. 
It  has  been  known  for  some  time,  for  instance,  that,  while  the  num- 
bers of  bacteria  are  generally  reduced  by  partial  sterilization,  later 
on  the  bacterial  population  rises  to  abnormal  proportions. 

The  different  views  held  on  this  subject  may  be  briefly  summarized 
under  three  heads.  First,  the  stimulation  theory,  by  which  it  is 
held  that  the  organisms  which  survive  receive  a  direct  stimulation 
from  the  treatment  in  addition  to  being  supplied  with  an  increase  in 
food,  made  available  by  the  sterilization,  through  decomposition  of 
the  soil  organic  matter,  and  in  the  cells  of  the  organisms  killed  by  the 
treatment.  Second,  the  protozoan  theory,  according  to  which  par- 
tial sterilization  causes  a  destruction  of  certain  phagocytes,  which  are 
supposed  to  feed  upon  the  bacteria  of  soils  and  thus  keep  their  num- 
bers, and  consequently  their  efficiency,  in  check.  The  amoebae, 
infusoria,  etc.,  being  killed  by  the  treatment,  the  remaining  bacteria 
then  multiply  to  great  numbers,  and  the  greater  numbers  of  bacteria 
thus  arising,  rather  than  increased  efficiency,  cause  the  production  of 
greater  amounts  of  available  nitrogen.  Third,  the  bacterio toxin 
and  soil-film  theory,  according  to  which  soils  may  contain  sub- 
stances poisonous  to  bacteria,  which  substances  are  capable  of  being 
decomposed  at  the  temperatures  employed  in  partial  sterilization  by 
means  of  heat.  Volatile  antiseptics,  on  the  other  hand,  bring  about 
bacterial  stimulation  through  the  solvent  effects  exerted  on  certain 
organic  substances  which  surround  the  soil  particles  and  which  par- 
tially waterproof  them,  thus  protecting  the  organic  substances  from 
the  attack  of  bacteria.  Upon  evaporating  the  antiseptic,  the  dis- 
solved substances  become  redistributed  in  such  way  as  to  leave  the 
soil  particles  more  open  to  bacterial  invasion. 

It  will  be  noted  that  all  but  one  of  the  theories  above  named  pre- 
suppose the  existence  of  a  limiting  agent  in  soils,  the  presence  of  one 
or  more  factors  which  operate  to  hold  in  check  bacterial  action. 
From  the  experiments  above  recorded  it  seems  that  the  uncultivated 
soils  of  Hawaii  contain  some  agent  which  limits  bacterial  action. 
It  was  shown,  for  instance,  that  the  low  bacterial  efficiency  is  not  due 
to  the  absence  of  oxygen  as  such,  nor  the  specific  organism,  but  rather 
to  the  presence  of  some  factor  which  is  susceptible  of  alteration  by 
aeration,  but  considerable  time  is  required  for  the  aeration  to  exert 
its  effects.  It  was  suggested,  therefore,  that  the  toxic  condition 
might  be  susceptible  of  alteration  by  partial  sterilization.  For  this 
reason  the  following  experiments  were  undertaken. 

In  these  experiments  the  methods  employed  by  Russell  and 
Hutchinson x  were  used.     The  soils  on  reaching  the  laboratory  were 

iJour.  Agr.  Sci.,  3(1909),  pp.  111-144;  also  Russell  and  Golding,  ibid.,  5  (1912),  pp.  27-47;  Russell  and 
Petherbridge,  5  (1912),  pp.  86-111;  Russell  and  Hutchinson,  ibid.,  5  (1913),  pp.  152-221. 


22 

spread  out  on  large  sheets  of  paper  and  after  becoming  air  dry, 
different  portions  were  treated  as  follows:  One  portion  of  each  soil 
containing  from  600  to  800  grams,  was  heated  in  a  water  oven  at 
98°  C.  for  two  hours,  then  immediately  placed  in  screw-cap  glass 
jars.  Other  portions  of  equal  weight  were  thoroughly  mixed  with 
toluol  and  carbon  bisulphid  at  the  rate  of  4  cubic  centimeters  per  100 
grams  of  soil,  then  placed  in  tight-fitting  screw-cap  jars,  in  which 
condition  the  sample  stood  for  three  days.  These  portions  were  then 
spread  out  in  thin  layers  on  clean  paper,  and  the  antiseptic  allowed 
to  evaporate  for  three  additional  days,  when  no  odor  of  the  antiseptic 
could  be#  detected.  The  treated  samples  and  also  an  untreated  por- 
tion of  each  soil  were  then  brought  to  optimum  moisture  by  adding 
sterile  water,  placed  in  large  fruit  jars,  loosely  stoppered,  and  kept  in 
a  dark  closet  at  about  28°  C.  The  moisture  was  maintained  by  the 
addition  of  sterile  water  from  time  to  time.  At  different  intervals 
portions  were  withdrawn  with  a  sterile  spatula,  and  the  nitrate  and 
ammonia  determined.     The  results  are  shown  in  the  following  table: 

Ammonia  and  nitrate  nitrogen  in  partially  sterilized  soils. 

[Parts  per  million  of  the  air-dried  soil.] 

AMMONIA  NITROGEN. 


Cultivated  soil  No.  329. 

Uncultivated  soil  No.  330. 

Treatment. 

Before 
treat- 
ment. 

After  8 
days. 

After  14 
days. 

After  21 
days. 

After  28 
days. 

Before 
treat- 
ment. 

After  8 
days. 

After  14 
days. 

After  21 
days. 

After  28 
days. 

Untreated 

Heated  to98°C 

Toluol 

33.6 
33.6 
33.6 

39.2 
104.8 
117.6 

22.4 
106.4 
114.8 

28.0 
128.8 
126.0 

33.6 
123.2 
131.6 

14.0 
14.0 
14.0 

19.6 
67.2 
89.6 

11.2 

72.8 

114.8 

22.4 
84.0 
120.4 

28.0 

78.4 
126  0 

NITRATE  NITROGEN. 


Untreated 

75.0 
75.0 
75.0 

220.0 
150. 0 
190.0 

220.0 
148.0 
180.0 

168.0 
140.0 
160.0 

220.0 
164.0 
65.0 

1.3 
1.3 
1.3 

ia.o 

5.0 

38.0 

14.6 

6.0 

34.8 

18.8 

5.0 

33.2 

7.0 

Heated  to  98°  C 

Toluol 

2.0 
27.0 

TOTAL  NITRATE  AND  AMMONIA  NITROGEN. 


Untreated 

Heated  to  98°  C 
Toluol 


108.6 
108.6 
108.6 

259.2 
254.8 
307.6 

242.4 
254.4 
294.8 

196.0 
268.8 
286.0 

253. 6 
287. 2 
196.6 

15.3 
15.3 
15.3 

32.6 

72.2 

127.6 

25.8 
78.8 
149.6 

41.2 
89.0 
153.6 

35.0 
80.4 
153.0 


GAINS   IN  NITRATE  AND  AMMONIA  NITROGEN. 


Untreated. 
Heated  to ! 
Toluol 


S°C. 


150.  6 
146.2 
199.0 


133. 
145. 


87.4 
160.2 
177.4 


145.0 
178.6 
88.0 


17.3 
56.9 
112.3 


10.5 
63.5 
134.3 


25.9 
73.7 
138.3 


19.7 
65.1 
137.7 


23 


Ammonia  and  nitrate  nitrogen  in  partially  sterilized  soils — Continued. 

AMMONIA    NITROGEN. 


Cultivated  soil  No.  416. 

Uncultivated  soil  No.  417. 

Treatment. 

At  the 
begin- 
ning. 

After  7 
days. 

After  14 
days. 

After  21 
days. 

After  28 
days. 

At  the 
begin- 
ning. 

After  7 
days. 

After  14 
days. 

After  21 
days. 

After  28 
days. 

Untreated 

19.6 
33.6 

22.4 

11.2 
86.8 
78.4 

14.0 
100.8 
100.8 

16.8 
106.4 
109.2 

28.0 
109.2 
120.4 

22.4 
32.8 
25.2 

53.2 
112.0 
120.4 

42.0 
14S.  4 
154.0 

48.8 
159.6 
162.4 

42.0 

Heated  to%°C 

Toluol 

168.0 
179.2 

NITRATE  NITROGEN. 


Untreated 

Heated  to  98°  C. 
Toluol 


70.0 

90.0 

92.0 

86.0 

90.0 

0.6 

0.6 

13.0 

8.8 

68.0 

65.0 

70.0 

64.0 

60.0 

.7 

2.3 

8.8 

.7 

60.0 

62.0 

64.0 

60.0 

60.0 

.4 

.5 

12.0 

.7 

12.0 
.6 


TOTAL  NITRATE  AND   AMMONIA  NITROGEN. 


Untreated 

89.6 
101.6 
82.4 

101.2 
151.8 
140.4 

106.0 
170.8 
164.8 

102.8 
170.4 
169.2 

118.0 
169.2 
180.4 

23.0 
33.5 
25.6 

53.8 
114.3 
120.9 

55.0 
157.2 
166.0 

57.6 
160.3 
163.1 

54.0 

Heated  to  98°  C 

Toluol 

168.6 
179.8 

GAINS   IN   NITRATE   AND   AMMONIA  NITROGEN. 


11.6 
50.2 
58.0 

16.4 
69.2 
82.4 

13.2 
68.8 
86.8 

28.4 
67.6 
98.0 

30.8 
80.8 
95.3 

32.0 
123.7 
140.4 

34.6 

126.8 
137.5 

31.0 

Heated  to  98°  C 

135.1 

Toluol 

154.2 

The  above  data  show  that  notable  effects  were  produced  by  partial 
sterilization.  For  instance,  as  a  result  of  the  treatment,  the  ammonia 
content  increased  in  both  cultivated  and  uncultivated  soils  during 
the  entire  28-day  period  of  observation.  Nitrification,  on  the  other 
hand,  was  totally  inhibited  in  soils  Nos.  416  and  417,  while  in  Nos.  329 
and  330  it  was  considerably  checked  in  most  instances.  The  data 
showing  the  gains  in  total  ammonia  and  nitrate  bring  out  the  effects 
more  correctly  since  the  nitrate  formed  must  have  passed  through 
the  ammonia  stage.  Cultivated  soil  No.  329  gained  33.6  parts  per 
million  as  a  result  of  heating,  while  the  uncultivated  soil  No.  330 
gained  45.4  parts.  Treatment  with  toluol  affected  ammonification  in 
soil  No.  329  very  much  the  same  as  heating,  while  in  No.  330  toluol 
produced  notably  greater  effects,  but  in  the  former  instances  denitri- 
fication  became  excessive,  the  nitrate  content  having  decreased, 
after  the  eighth  day,  from  190  parts  to  65  parts  per  million.  Some 
denitrification  took  place  in  soil  No.  330,  although  to  a  much  less 
extent. 

Considering  soils  Nos.  416  and  417,  we  find  that  partial  sterilization 
produced  similar  effects  in  both  the  cultivated  and  uncultivated 
soils,  causing,  on  the  one  hand,  a  marked  stimulation  in  the  ammoni- 
fication and,  on  the  other,  totally  preventing  nitrification.  It  is  also 
noteworthy  that  at  the  end  of  28  days  the  total  nitrate  and  ammonia 


24 


nitrogen  in  the  treated  portions  of  the  cultivated  and  uncultivated 
soils  was  practically  the  same.  Ammonincation  was  therefore  the 
more  markedly  stimulated  in  the  uncultivated  soil,  since  the  available 
nitrogen  originally  present  was  considerably  less  than  in  the  culti- 
vated soil. 

In  order  to  determine  whether  effects  similar  to  those  observed 

above  would  be  produced  in  other  island  soils,  the  same  treatments 

were  applied  to  a  soil  from  the  experiment  station  grounds,  No.  288, 

and  to  a  rice  soil,  No.  292,  which  was  previously  devoted  to  rice 

experiments  by  this  station.     The  results  follow: 

Effects  of  partial  sterilization. 

[Parts  per  million.] 

AMMONIA  NITROGEN. 


Soil  No.  288. 

Soil  No.  292. 

Treatment. 

Before 
treat- 
ment. 

After 

8 
days. 

After 

14 
days. 

After 

21 
days. 

After 

28 
days. 

Before 
treat- 
ment. 

After 

7 
days. 

After 

14 
days. 

After 

21 
days. 

After 

28 
days. 

After 

35 
days. 

Untreated 

16.8 
16.8 
16.8 

28.0 
44.8 
36.4 

11.2 
39.2 
11.2 

16.4 
39.2 
14.0 

14.0 
22.4 
19.6 

2.0 
2.0 
2.0 

19.6 
33.6 
30.8 

14.0 
39.2 
30.8 

11.2 
36.4 
16.8 

11.2 
42.0 
11.2 

14.0 

Heated  to  98°  C 

Toluol 

47.6 
16.8 

NITRATE   NITROGEN. 

4.7 
4.7 
4.7 

36.0 
28.0 
32.0 

44.0 
37.2 
68.0 

40.0 

42.0 

139.0 

40.0 
67.0 
70.0 

0.5 
.5 
.5 

24.0 
6.5 
1.4 

27.5 
14.5 
14.5 

33.4 
16.0 
25.0 

37.6 

24.8 
38.0 

47.0 

Heated  to  98°  C 

Toluol 

26.5 
47.0 

TOTAL  AMMONIA  AND  NITRATE  NITROGEN. 

21.5 
21.5 
21.5 

64.0 

72.8 
68.4 

55.2 
76.4 
79.2 

56.4 
81.2 
53.0 

54.0 

89.4 
89.6 

2.5 
2.5 
2.5 

43.6 
40.1 
32.2 

41.5 
53.7 
45.3 

44.6 
52.4 
41.8 

48.8 
66.8 
49.2 

61.0 

Heated  to  98°  C 

Toluol 

74.1 

63.8 

GAINS  IN  AMMONIA  AND  NITRATE  NITROGEN. 

Untreated 

42.5 
51.3 
46.9 

33.7 
54.9 

57.7 

34.9 
59.7 
31.5 

32.5 
67.9 
68.1 

41.1 
37.6 

29.7 

39.0 
51.2 

42.8 

42.1 
49.9 
39.3 

46.3 
64.3 
46.7 

58.5 

Heated  to  98°  C 

71.6 

Toluol 

61.3 

i  Too  low,  probably  due  to  error  of  determination. 

Thus  it  is  shown  that  ammonincation  was  greatly  stimulated  in 
soil  No.  288  by  heating  to  98°  C.  and  by  the  addition  of  toluol.  But 
the  ammonia  was  prevented  from  accumulating  toward  the  close  of 
the  experimental  period  by  the  activity  of  nitrification,  whereas  nitri- 
fication was  partially  inhibited  in  soil  No.  292.  The  total  ammonia 
and  nitrate  present  at  the  different  intervals  show  that  an  increase 
in  the  amounts  of  available  nitrogen  was  produced  by  partial  steril- 
ization, but  the  effectiveness  of  the  treatment  was  much  greater  in 
the  soil  from  the  experiment  station  grounds  than  in  the  rice  soil. 
In  fact,  the  total  ammonia  and  nitrate  at  the  different  intervals  in 
the  portions  of  soil  No.  292  treated  with  toluol  were  practically  the 


25 

same  as  those  in  the  untreated  portions,  while  the  increases  in  the 
heated  portions  were  small.  The  effects  produced  with  soil  No.  288, 
on  the  other  hand,  were  notable,  amounting  to  more  than  100  per  cent 
increases  in  the  available  nitrogen. 

The  conclusion  to  be  drawn  from  the  above  experiments  is  that 
ammonification  in  Hawaiian  soils  may  be  greatly  stimulated  by  par- 
tial sterilization,  and  that,  in  a  few  instances,  stimulation  may  result 
in  nitrification,  although  it  is  temporarily  inhibited. 

It  is  claimed  by  Russell  and  Hutchinson  !  that  the  stimulation 
given  to  ammonification  by  partial  sterilization  maybe  slowly  over- 
come by  reinoculation  with  a  small  portion  of  the  original  soil.  They 
found,  for  example,  that  the  numbers  of  bacteria  in  the  reinoculated 
portions  decreased,  gradually  diminishing  in  numbers  until  approxi- 
mately the  same  numbers  were  found  as  in  the  untreated  soil,  and 
that  the  ammonia  content  also  decreased,  the  amounts  found  being 
roughly  proportional  to  the  number  of  bacteria  present.  They 
attribute  these  phenomena  to  the  reintroduction  into  the  treated  soil 
of  the  hmiting  agent  (believed  by  them  to  be  protozoa)  that  occurs  in 
natural  soils,  which  agent,  they  hold,  is  destroyed  by  partial  steriliza- 
tion. For  the  purpose  of  studying  the  effects  thus  produced  in 
Hawaiian  soils,  the  same  treatments  as  were  employed  in  the  previous 
experiments  were  applied  to  different  soils,  and  they  were  reinoculated 
by  adding  5  per  cent  by  weight  of  the  original  soil.  Observations 
over  a  much  longer  period  than  was  employed  in  the  previous  experi- 
ments were  made  and  optimum  moisture  conditions  maintained 
throughout.     The  results  are  recorded  in  the  following  tables: 

Effects  of  partial  sterilization,  soil  No.  428. 

[Parts  per  million.] 

AMMONIA  NITROGEN. 


Treatment. 


At  the 

begin- 
ning. 

After 

After 

After 

After 

After 

After 

138 
days. 

7  days. 

14  days. 

21  days. 

35  days. 

63  days. 

106.4 

123.2 

123.2 

95.2 

75.6 

5.6 

5.6 

103.  G 

128.  s 

141.7 

159.6 

171.6 

207.2 

159.6 

103.4 

137.2 

145.6 

154.  0 

162.4 

16.8 

2.8 

100.8 

151.2 

154.0 

170.8 

182.0 

210.0 

120.4 

100.  s 

154.0 

148.4 

170.8 

171.6 

11.0 

5.6 

98.0 

126.0 

142.8 

156.  4 

164.0 

210.0 

210.  s 

98.0 

137.2 

145.6 

168.0 

164.0 

204.4 

168.0 

After 

201 

days. 


Untreated 

Heated  to  98°  C 

Heated  -|-  5  per  cent  original  soil . 

Toluol  4  per  cent 

Toluol  +  5  per  cent  original  soil. . 

CS2  4  per  cent 

CS2  4-  5  per  cent  original  soil 


14.0 
11.2 

ltl.  1 
22.4 
11.0 

11.2 


NITRATE  NITROGEN. 


Untreated 

Heated  to  98°  C 

Heated  +  5  per  cent  original  soil . 

Toluol  4  per  cent 

Toluol  +  5  per  cent  original  soil. . 

CS2  4  per  cent 

CS2  +  5  per  cent  original  soil 


5ft  5 

74.0 

68.  0 

88.0 

91.0 

225.0 

310.0 

53. 5 

64.0 

67.5 

58.  0 

77.  5 

160.0 

53.5 

64.0 

62.0 

60.0 

235.  0 

380.0 

54.5 

62.0 

60.0 

75.  0 

180.0 

54.5 

64.0 

62.0 

60.0 

60.0 

232.  5 

2'. HI.  0 

56.0 

61.0 

64.0 

56.0 

72.0 

80.0 

55.0 

60.0 

62.0 

64.0 

62.0 

67.5 

185.0 

330.  0 
280.6 

:;;o.o 

26a  e 
75. 0 

290.0 


1  Loc.  cit. 


73729°— 


26 


Effects  of  partial  sterilization,  soil  No.  428 — Continued. 

TOTAL  NITRATE  AND  AMMONIA  NITROGEN. 


Treatment. 


At  the 
begin- 
ning. 


After 
7  days. 


After 
14  days 


After 
21  days. 


After 
35  days, 


After 
63  days. 


After 

138 

days. 


After 

201 
days. 


Untreated : 

Heated  to  98°  C 

Heated  +  5  per  cent  original  soil 

Toluol  4  per  cent 

Toluol  +  5  per  cent  original  soil. 

CS2  4  per  cent 

CS2  +  5  per  cent  original  soil 


161.9 
157.1 
156.9 
155.3 
155.3 
153.0 
153.0 


197.2 
192.8 
201.2 
215.2 
218.0 
182.0 
197.2 


191.2 
209.2 
207.6 
216.0 
210.4 
206.8 
207.6 


183.2 
217.6 
210.0 
226.8 
230.8 
220.4 
232.0 


169.6 
227.6 
222.4 
242.  0 
231.6 
220.0 
226.0 


230.6 
284.8 
251.8 
285,0 
246.5 
282.0 
271.9 


315.6 
319.6 
382.8 
300.4 
295. 6 
320.8 
353.0 


344.0 
291.2 
356.4 
282.4 
344.0 
343.8 
301.2 


GAINS  IN  NITRATE  AND  AMMONIA  NITROGEN. 


Untreated 

Heated  to  98°  C 

Heated  +  5  per  cent  original  soil. 

Toluol  4  per  cent 

Toluol  +  5  per  cent  original  soil. . 

CS2  4  per  cent 

CS2  +  5  per  cent  original  soil 


35.3 
35.7 
44.3 
59.9 
62.7 
29.0 
44.2 


29.3 
52.1 
50.7 
60.7 
55.1 
53.8 
54.6 


21.3 
60.5 
53.1 
71.5 
75.5 
67.4 
79.0 


7.7 
70.5 
65.5 
86.7 
76.3 
67.0 
73.0 


08.  ( 
127.7 

94.9 
129.7 

91.2 
129.0 
118.9 


153.  7 
162.5 
225.9 
145.1 
140.3 
167.8 
200.0 


182.1 
134.1 
199.5 
127.1 
188.7 
190.8 
148.2 


Effects  of  partial  sterilization,  soil  No.  485. 
[Parts  per  million.] 
AMMONIA  NITROGEN. 


Treatment. 


Untreated 

Heated  to  98°  C 

Heated  +  5  per  cent  original  soil 

Toluol  4  per  cent 

Toluol  +  5  per  cent  original  soil. 

CS2  4  per  cent 

CS2  +  5  per  cent  original  soil 


Before 
treat- 
ment. 


7.0 
7.0 
7.0 
7.0 
7.0 
7.0 
7.0 


After 
7  days. 


8.4 
36.4 
39.2 
47.6 
42.0 
44.8 
42.0 


After 
14  days. 


16.8 
56.0 
44.8 
61.6 
56.0 
64.4 
61.6 


After 
21  days. 


14.0 
46.7 
39.2 
61.6 
33.6 
67.2 
67.2 


After 
28  days, 


22.4 
22.4 
8.4 
33.6 
14.0 
70.0 
70.0 


After 
35  days. 


8.4 
16.8 
11.2 
11.2 
11.2 
70.0 
72.8 


After 
94  days. 


8.4 
5.6 
2.8 
8.4 
8.4 
86.8 
11.2 


After 

156 
days. 


14.0 
11.2 
14.0 
11.2 
14.0 
75.6 
11.2 


NITRATE  NITROGEN. 


Untreated 

Heated  to  98°  C 

Heated  +  5  per  cent  original  soil 

Toluol  4  per  cent 

Toluol  +  5  per  cent  original  soil. 
CS2  4  per  cent 

CS2  +  5  per  cent  original  soil . . . 


10.0 

18.0 

23.5 

30.0 

30.0 

32.0 

62.5 

10.0 

13.0 

15.0 

30.0 

66.0 

82.5 

92.5 

10.0 

14.8 

20.0 

32.5 

70.0 

75.0 

92.5 

10.0 

10.0 

8.4 

16.0 

36.0 

65.0 

80.0 

10.0 

12.0 

14.8 

27.5 

62.0 

72.5 

97.5 

10.0 

1.0 

2.8 

5.7 

7.6 

8.0 

10.6 

10.0 

2.5 

5.0 

8.5 

8.6 

9.8 

97.5 

87.5 
120.0 
117.5 
100.0 
105.  0 
31.5 
83.5 


TOTAL   NITRATE   AND   AMMONIA   NITROGEN. 


Untreated 

Heated  to  98°  C 

Heated  +  5  per  cent  original  soil 

Toluol  4  per  cent 

Toluol  +  5  per  cent  original  soil. 

CS2  4  per  cent 

CS2  +  5  per  cent  original  soil 


17  0 

26.4 

40.3 

44.0 

52.4 

40.4 

70.9 

17.0 

49.4 

71.0 

76.7 

88.4 

99.3 

98.1 

17.0 

54.0 

64.8 

71.7 

78.4 

86.2 

95.3 

17.0 

57.6 

70.0 

77.6 

69.6 

76.2 

88.4 

17.0 

54.0 

70.8 

61.1 

76.0 

83.7 

105.  9 

17.0 

45.8 

67.2 

72.9 

77.6 

78.0 

97.4 

17.0 

44.5 

66.6 

,.).  1 

78.  6 

82.6 

108.7 

101.5 
131.2 
131.5 
111.2 
119.0 
107.1 
94.7 


GAINS   IN   NITRATE   AND   AMMONIA   NITROGEN. 


Untreated 

9.4 
32.4 
37.0 
40.6 
37.0 
28.8 
27.5 

23.3 
54.0 
47.8 
53.0 
53.8 
50.2 
49.6 

27.0 
59.7 
54.7 
60.6 
44.1 
55.9 
58.7 

35.4 
71.4 
61.4 
52.6 
59.0 
60.6 
61.6 

23.4 
82.3 
69.2 
59.2 
66.7 
61.0 
65.6 

53.9 
81.1 
78.3 
71.4 
88.9 
80.4 
91.7 

84.5 

Heated  to  98°  C 

114.2 

Heated  +  5  per  cent  original  soil .... 

114.5 

Toluol  4  per  cent 

94.2 

Toluol  +  5  p;r  cent  original  soil 

102.0 

CS2  4  per  cent 

90.1 

CS2  -1-  5  per  cent  original  soil 

77.  7 

i 


27 


Effects  of  -partial  sterilization,  soil  No.  486. 

[Parts  per  million.] 

AMMONIA   NITROGEN. 


Treatment. 


Before 
treat- 
ment. 


Untreated 

Heated  to  98°  C 

Heated  +  5  per  cent  original  soil 

Toluol  4  per  cent 

Toluol  -f  5  per  cent  original  soil 

CS2  4  per  cent 

CS2  +  5  per  cent  original  soil 


8.0 
8.0 
8.0 
8.0 
8.0 
8.0 
8.0 


After 
7  davs. 


B.  I 
72.8 

70.0 

78.4 
70.0 
64.6 

72.8 


After 
14  days 


14.0 
100.8 
81.2 
9S.0 
89.6 
89.6 
100.8 


After 
21  days. 


14.0 
84.0 
72.8 
103.6 
100.8 
95.2 
95.2 


After 
28  days. 


After 
35  clays. 


11.2 
39.  2 
16.8 

106.4 
.")().  4 
95.2 

106.2 


14.0 
16.8 
16.9 

117.6 
16.8 
100.  8 

111'.  2 


After 
94  days. 


16.8 
8.4 

16.8 
8.4 

11.2 
114.8 

11.2 


After 

156 

days. 


11.2 
14.0 
14.0 
11.2 
14.0 
112.0 
11.2 


NITRATE   NITROGEN. 


Untreated 

Heated  to  98°  C 

Heated  +  5  per  cent  original  soil . 

Toluol  4  per  cent 

Toluol  +  5  per  cent  original  soil. 

CS2  4  per  cent 

CS2  +  5  per  cent  original  soil 


6.0 

18.0 

20.0 

25.0 

25.0 

34.0 

70.0 

6.0 

14.0 

10.0 

19.0 

55.0 

102.5 

107.5 

6.0 

s.o 

14.0 

26.0 

64.0 

90.0 

117.5 

6.0 

5.0 

5.8 

5.5 

5.5 

7.5 

90.0 

6.0 

5.0 

7.0 

9.0 

40.0 

91.0 

120.0 

6.0 

0.5 

2.0 

2.5 

3.0 

3.0 

7.6 

6.0 

0.5 

2.0 

3.0 

3.0 

2.8 

102.5 

87.5 
170.0 
140.0 
140.0 
135.0 

22.0 
130.0 


TOTAL  NITRATE   AND   AMMONIA   NITROGEN. 


Untreated 

Heated  to  98°  C 

Heated  +  5  per  cent  original  soil. 

Toluol  4  per  cent 

Toluol  +  5  per  cent  original  soil . . 
CS2  4  per  cent 

CS2  +  5  per  cent  original  soil 


14.0 

26.4 

34.0 

39.0 

36.2 

48.0 

86.8 

14.0 

86.8 

110.8 

103.0 

94.2 

119.3 

115.9 

14.0 

78.0 

95.2 

98.9 

80.8 

106.8 

134.  3 

14.0 

83.4 

103.8 

109.1 

111.9 

125. 1 

98.4 

14.0 

75.0 

96.6 

109.8 

90.4 

107.  S 

131.  2 

14.0 

65. 1 

91.6 

97.7 

98.2 

103.8 

122.  4 

14.0 

73.3 

102.8 

98.2 

109.4 

112.0 

113.7 

98.7 
184.0 
154.  0 
151.2 
149.0 
134.0 
141.2 


GAINS   IN   NITRATE    AND   AMMONIA   NITROGEN. 


Untreated 

Heated  to  98°  C 

Heated  +  5  per  cent  original  soil. 

Toluol  4  per  cent 

Toluol  +  5  per  cent  original  soil . 

CS2  4  per  cent " 

CS2  +  5  per  cent  original  soil 


12.4 
72.8 
64.0 
69.4 
61.0 
51.1 
59.3 


20.0 
96.8 
81.2 
89.8 
82.6 
77.6 


2.5.0 
89.0 
84.9 
95.1 
95.8 
83.7 
84.2 


22.2 
80.2 
66.8 
97.9 
76.4 
84.2 
95.4 


34. 
105. 

92. 
111. 

93. 

89. 

98. 


72.8 
101.9 
120.3 

84.4 
117.2 
108.4 

99.7 


84.7 
170.0 
140.0 
137.2 
135. 0 
120. 0 
127.2 


It  will  be  seen  that  in  each  soil  an  increase  in  the  ammonia  content 
was  effected  by  partial  sterilization,  but  that  after  the  lapse  of  a  cer- 
tain interval  of  time,  varying  in  the  different  soils  studied,  and  also 
in  the  same  soil  when  partially  sterilized  by  different  means,  nitrifi- 
cation set  in,  with  the  result  that  the  ammonia  content  became 
reduced  to  a  low  and  practically  equal  concentration  in  all  the  differ- 
ent  portions  of  each  soil,  with  the  exception  of  those  treated  with 
carbon  bisulphid.  In  this  case  the  ammonia  content  increased 
throughout  the  time  of  observation,  only  slight  nitrification  having 
taken  place,  and  then  only  after  a  lapse  of  several  months.  The 
addition  of  5  per  cent  of  the  original  soil  to  the  partially  sterilized 
portions  produced  more  vigorous  nitrification  in  the  early  periods, 
due  no  doubt  to  the  introduction  of  active  nitrifying  organisms.  The 
method  of  effecting  partial  sterilization  probably  killed  the  greater 
numbers  of  the  nitrifying  organisms  present ,  as  has  been  shown  to  take 
place  by  Russell  and  Hutchinson  and  others. 


28 

The  total  ammonia  and  nitrate  present  is  of  especial  interest.  It  is 
noteworthy  that  in  soil  No.  428  partial  sterilization  produced  a  con- 
siderable increase  in  the  available  nitrogen  at  the  different  intervals 
up  to  63  days  from  the  time  of  treatment.  After  this  time  the  avail- 
able nitrogen  continued  to  accumulate  up  to  the  138th  day,  but  at 
rates  correspondingly  less  in  the  treated  than  in  the  untreated  por- 
tions. Consequently  the  gains  in  available  nitrogen  during  this 
period  were  less  than  during  earlier  periods.  From  the  138th  to  the 
201st  day,  most  of  the  partially  sterilized  portions  lost  available 
nitrogen,  whereas  the  accumulation  continued  in  the  untreated  por- 
tions; consequently  at  the  end  of  the  experimental  period  the 
untreated  portions  contained  more  nitrate  and  ammonia  than  a  num- 
ber of  treated  portions. 

It  will  also  be  noted  that  reinoculation  with  5  per  cent  of  the  orig- 
inal soil  of  the  portions  heated  and  treated  with  toluol  caused  an 
increase  in  available  nitrogen,  but  in  the  carbon  bisulphid  portions 
exactly  opposite  effects  were  produced,  that  is,  reinoculation  resulted 
in  a  notable  decrease  in  the  available  nitrogen. 

Turning  to  soils  Nos.  485  and  486,  it  will  be  seen  that  the  partial 
sterilization  stimulated  ammonification  throughout  the  experiment. 
Reinoculating  the  portions  of  No.  485,  heated  and  treated  with 
toluol,  and  the  portions  of  No.  486,  treated  with  toluol  and  carbon 
bisulphid,  on  the  whole  produced  no  effects,  while  the  reinoculation 
of  No.  485,  treated  with  carbon  bisulphid,  and  the  heated  portion  of 
No.  486  caused  a  considerable  reduction  in  the  total  nitrate  and 
ammonia.  On  the  whole,  then,  the  effects  produced  by  reinoculating 
the  partially  sterilized  soils  are  not  in  harmony  with  those  found  by 
Russell  et  al. 

It  has  been  shown  by  Gainey  1  that  the  use  of  small  amounts  of 
antiseptics  results  in  immediate  stimulation  of  the  bacteria  without 
a  reduction  in  the  numbers  present,  such  as  takes  place  where  larger 
amounts  are  used.  Gainey  further  found  that  the  application  of 
different  volatile  antiseptics  produced  notable  stimulation  in  the 
growth  of  crops,  but  he  failed  to  detect  a  corresponding  effect  on  the 
numbers  of  bacteria  present.2 

In  the  experiments  reported  above,  the  antiseptic  was  allowed  to 
evaporate  frtfm  the  soil  until  no  further  odor  could  be  detected.  The 
treatments  were  made  on  air-dried  soils,  but,  upon  bringing  to  opti- 
mum moisture  content  and  allowing  to  stand  a  few  days,  a  faint  odor 
of  the  antiseptics  was  detected  in  most  instances.  Where  carbon 
bisulphid  was  employed  rather  distinct  odors  of  the  substance  were 
noticed  till  near  the  close  of  the  period  of  observation.     Since  it  has 

i  Missouri  Bot.  Gard.,  Ann.  Rpt.,  23  (1912),  pp.  147-169. 

2  In  Gainey's  experiments  the  moisture  content  of  the  soil  was  brought  to  one-third  or  one-half  satura- 
tion before  the  antiseptic  was  added,  and  since  the  substances  used  are  miscible  with  water  to  a  slight 
extent  only,  it  is  possible  that  the  different  organisms  present  did  not  come  in  contact  with  the  antiseptics. 


29 


been  shown  that  Hawaiian  soils  have  a  remarkably  high  absorptive 
capacity  l  it  was  suggested  that  the  treated  portions  absorbed  small 
amounts  of  the  antiseptics,  which  exerted  stimulative  effects  on  the 
surviving  bacteria.  As  shown  in  the  preceding  tables,  where  carbon 
bisulphid  was  employed,  nitrification  did  not  set  in  until  after  a  much 
longer  time  than  when  other  methods  of  effecting  partial  sterilization 
were  used.  This  may  have  been  due  to  the  inhibiting  action  of  the 
carbon  bisulphid  absorbed. 

The  soils  employed  in  the  following  experiment  were  Nos.  288  and 
329,  the  same  as  employed  previously,  each  of  which  had  been  found 
to  show  marked  effects  from  partial  sterilization.  The  portions  used 
in  previous  experiments  were  treated  soon  after  becoming  air  dry. 
In  the  following  experiments,  however,  the  soils  had  remained  in  the 
laboratory  in  the  air-dried  state  for  several  months  previous  to  the 
time  of  treatment.     In  the  following  table  are  shown  the  results: 

Effects  of  partial  sterilization  on  thoroughly  desiccated  soils. 

[Parts  per  million.] 

AMMONIA  NITROGEN. 


Soil  N 

0.  288. 

Soil  No.  329. 

Treatment. 

At  the 
begin- 
ning. 

After 

15 
days. 

After 

33 
days. 

After 

82 
days. 

At  the 
begin- 
ning. 

After 

15 
days. 

After 

33 
days. 

After 

80 
days. 

Untreated 

19.6 
19.6 
19.6 
16.2 
19.6 

19.6 
19.6 
16.2 
16.2 

22.4 
25.2 
16.2 
33.6 
00.0 

00.0 
36.4 
42.0 
39.2 

5.6 
44.8 
25.2 
44.8 

8.4 

5.6 
58.8 
70.0 

58.8 

2.8 
5.6 
5.6 
5.6 

8.4 

5.6 
89.6 
84.0 
72.8 

56.0 
61.6 
61.6 
61.6 
64.4 

64.4 
70.0 
70.0 
70.0 

72.8 
72.8 
72.8 
50.4 
64.4 

72.8 

103.6 

61.6 

75.6 

89.6 
103.6 
95.2 
84.0 
75.6 

92.4 
84.0 
84.0 
92.4 

50.4 

Heated  to  98°  C 

128.8 

Heated+5  per  cent  original  soil 

Toluol  0.2  per  cent 

140.0 
131.6 

Toluol  4  per  cent 

100.8 

Toluol  4  per  cent+5  per  cent  original 
soil 

109.  i 

CS2  0.2  per  cent 

126.3 

CS2  4  per  cent 

162.1 

CS2  4  per  cent+5  per  cent  original  soil . 

162.4 

NITRATE  NITROGEN. 


Untreated 

Heated  to  98°  C 

Heated  to  98°  C.+5  percent  original 

soil 

Toluol  0.2  per  cent 

Toluol  4  per  cent 

Toluol  4  per  cent+5  per  cent  original 

soil 

CS2  0.2  per  cent 

CS2  4  per  cent 

CS2  4  per  cent+5  per  cent  original  soil 


17.5 
16.0 

41.0 
51.0 

50.0 
52.5 

120.0 
115.0 

152.0 
164.0 

137.5 
137.5 

195.0 
185.0 

16.0 
18.0 
16.8 

28.5 
21.0 
46.0 

52.0 
36.0 
55.0 

115.  b 

110.0 
110.0 

164.0 
160.0 
160.0 

145.0 
124.0 
150.0 

195.0 
180.0 
195.0 

16.8 
10.0 
4.5 
4.5 

35.0 

12.5 

1.0 

1.0 

60.0 
20.0 
5.5 

5.0 

120.0 

48.0 

35.0 

3.0 

160.0 
130.0 
160.0 
160.0 

137.5 
145. 0 
147.0 
132.5 

185.0 
185.0 
175.0 
170.  a 

280.0 
250.0 

205.0 
220.0 
225.0 

200.0 
180.0 
130.0 
135.0 


TOTAL  NITRATE  AND  AMMONIA  NITRON  EN. 


Untreated 

Heated  to  98°  C 

Heated  to  98°  C.+5  per  cent  original 

soil 

Toluol  0.2  per  cent 

Toluol  4  per  cent 

Toluol  4  per  cent+5  per  cent  original 

soil 

CS2  0.2  per  cent 

CS2  4  per  cent 

CS2  4  per  cent+5  per  cent  original  soil 


37.1 
•    35.6 

63.4 
76.2 

55.6 
97.3 

122.8 
120.6 

208.0 
225.6 

210.3 
210.3 

284.6 
288.6 

35.6 
34.2 
36.4 

44.7 
54.6 
46.0 

77.2 
80.8 
63.4 

120.6 
115.6 

118.4 

225.6 
221.6 
224.4 

217.8 
174.4 
214.4 

290.2 
264.0 
270.6 

36.4 
29.6 
20.7 
20.7 

35.0 
48.9 
43.0 
40.2 

65.6 
78.8 
75.5 
63.8 

125.6 
137.  6 
119.0 
75.8 

224.4 
200.0 
230.0 
230.0 

*210.3 
248.6 
206.  6 

208.1 

277.4 
269.0 
259. 0 
262.4 

330.4 
378.8 

345.0 
351.6 
325.8 

309.2 
306.0 
292.4 
297.4 


»  Hawaii  Sta.  Bui.  35. 


30 


Effects  of  partial  sterilization  on  thoroughly  desiccated  soils — Continued. 

GAIN  (+)  OR  LOSS  (-)  IN  NITRATE  AND  AMMONIA  NITROGEN. 


Treatment. 


Soil  No.  288. 


At  the 
begin- 
ning. 


Untreated 

Heated  to  98°  C ■ 

Heated  to  98°  C. +5  per  cent  original 

soil 

Toluol  0.2  per  cent 

Toluol  4  per  cent . 

Toluol  4  per  cent+5  per  cent  original 

soil 

CS2  0.2  per  cent 

CS2  4  per  cent 

CS2  4  per  cent+5  per  cent  original  soil 


After 

15 
days. 


+26.3 
+40.6 


+  9.1 
+20.4 


-1.4 
+19.3 
+22.3 
+  19.5 


After 

33 
days. 


+18.5 
+61.7 

+41.6 
+46.6 
+27.0 

+29.2 
+49.2 
+54.8 
+43.1 


After 

82 
days. 


+  85.7 
+  85.0 

+  85.0 
+  81.4 
+  82.0 

+  89.2 
+108.0 
+  98.3 
+  55.1 


Soil  No.  329. 


At  the 
begin- 
ning. 


After 

15 
days. 


+  2.3 
-15.3 

-7.8 
-47.2 
-10.0 

-14.1 

+48.6 
-21.4 
-21.9 


After 

33 
days. 


+76.6 
+63.0 

+64.6 
+42.4 
+46.2 

+53.0 
+69.0 
+29.0 
+32.4 


After 

80 
days. 


+122.4 
+  153.2 

+  119.4 
+  130.0 
+  101.4 

+  84.8 
+106.0 
+  62.4 
+  67.4 


The  above  data  show  that  greater  irregularity  resulted  from  the 
treatments  than  in  any  of  the  previously  recorded  experiments.  At 
the  end  of  15  days  no  important  increase  in  available  nitrogen  was 
found,  except  in  the  heated  portions  of  soil  No.  288  and  the  portions 
of  No.  329  treated  with  0.2  per  cent  carbon  bisulphid.  On  the  other 
hand,  a  decrease  was  observed  in  a  number  of  instances.  At  that  time 
the  portions  of  No.  288  treated  with  carbon  bisulphid  contained  prac- 
tically no  nitrate.  After  33  days  each  of  the  treated  portions  con- 
tained an  increased  amount  of  available  nitrogen,  whereas  no  stimula- 
tion was  manifest  in  soil  No.  329,  and  after  82  days  no  increase  was 
found  in  any  instance  except  the  portion  of  No.  288  treated  with  0.2 
per  cent  carbon  bisulphid  and  those  of  No.  329  heated  and  treated 
with  toluol.  Reinoculating  the  portions  of  No.  288  treated  with 
toluol  was  without  effect,  whereas  in  No.  329  it  caused  a  reduction  of 
from  325.8  to  309.2  parts  per  million.  The  use  of  0.2  per  cent  of  both 
toluol  and  carbon  bisulphid  proved  equally  as  effective  as  4  per  cent. 

It  is  notable  that  irregular  and  sometimes  negative  effects  were 
produced  by  partial  sterilization  when  applied  after  the  soils  had  been 
air  dry  for  several  months,  while  the  same  treatment  applied  to  the 
fresh  soils  produced  regular  and  stimulating  effects. 

Before  taking  up  the  general  discussion  of  the  foregoing  results,  it 
will  be  of  interest  to  examine  the  data  already  submitted,  with  a 
view  to  determining  how  long  the  stimulation  continued  in  the 
different  soils  studied.  In  the  table  following  the  data  presented  in 
the  preceding  tables  are  brought  together  for  the  purpose  of  showing 
the  gains  in  available  nitrogen  during  the  different  periods. 


31 


Gain  (+)  or  loss  (  — )  in  ammonia  and  nitrate  nitrogen  during  successive  periods. 

[Parts  per  million.] 


Soil  No.  329. 

Soil  No.  330. 

Treatment. 

Davs     Davs 
1-8.       8-14, 

Davs     Davs 
14-21. 

Davs 
8-28. 

Days 
14-28. 

Davs 
1-8. 

Davs 
8-14. 

Days  |  Days 
14-21. 

Davs 

8-28. 

Davs 
14-28. 

Check 

+  150.61  -16.8 
+146.21  -     .4 
+  199.0    -12.8 

-46.  i 

+  14.4 
-  8.8 

+57.6 

-    5.6 

+  11.2 
+32.8 
-98.2 

-  17.: 

+15.  1    -6.2 

+  2.4 
+  8.2 
+25.4 

+  9.2 

Heated 

Toluol 

+  18.4+  32.4 
-89.4-111.0 

-  6.6    +10.2 
+  li.         +22.0    +  4.0 

-  8.6 

-  .6 

+  1.6 
+  3.4 

Soil  No.  416. 

Soil  No.  417. 

Treatment. 

Davs     Davs 
1-7.        7-14. 

Davs     Davs 
14-21.    21-28. 

Days 

7-28. 

Davs 
14-28. 

Days 
1-7. 

Davs 
7-14. 

Davs 
14-21. 

Davs 
21-28. 

Davs 

7-28. 

Days 
14-28. 

Check 

+  11.0    +4.8 

-  3.2 

-  .4 

+  4.4 

+  15.2 
-  1.2 
+11.2 

+16.8 
+17.4 

+12.0 
-  1.6 

+  30.8 
+  80.8 
+  95.3 

+  1.2 
+42.9 
+45.1 

+  2.fi 
+  3.1 
-  2.9 

-  3.6 
+  8.3 
+  16.7 

+  0.2 
+54.3 
+58.9 

-  1.0 

Heated 

+50.2 
+58.0 

+  19.0 
+24.4 

+  11.4 

Toluol 

+40.0    +15.6 

+  13.8 

Soil  No.  428. 


Treatment. 

Davs 
1-7. 

Days 
7-14. 

Davs 
14-21. 

Davs 
21-35. 

Davs 
35-63. 

Davs 
63-1*38. 

Davs 
138-201. 

Davs 
7-201. 

Days 
14-201. 

Check 

+35.3 

-  6.0 
+  16.4 

+  6.4 

+     .8 

-  7.6 
+24.8 
+  10.4 

■  -  8.0 
+  8.4 

+  2.4 
+  10.8 

+20.4 
+  13.6 
+24.4 

-13.6 
+  10.0 

+12.4 
+  15.2 

+     .8 

-  .4 

-  6.0 

+61.0 
+57.2 

+29.4 
+43.0 

+  14.9 
+62.0 
+45.9 

+  85.0 
+  34.8 

+  131.0 
+  15.4 

+  49.1 

+  38.8 
+  81.1 

+28.4 
-28.4 

-26.4 
-18.0 

+48.4 
+23.0 
-51.8 

+146.8 
+  98.4 

+  155.2 
+  67.2 

+  126.0 
+161.8 
+  104.0 

+  152.8 

Heated 

+35.7 

+44.3 
+59.9 

+62.7 
+29.0 

+  82.0 

Heated +5  per  cent  original 

+148.8 

Toluol 

+  66.4 

Toluol+5  per  cent  original 
soil 

+  133.6 

CS2 

+  137.0 

CSs+5  per  cent  original  soil. . 

+44.2 

+  93.6 

Soil  No.  485. 

Treatment. 

Days 

1-7. 

Davs 
7-14. 

Davs 
14-21. 

Days 
21-28. 

Days 
28-35. 

Days 
35-94. 

Davs 
94-^156. 

Davs 
7-156. 

Davs 
14-156. 

Check 

+  9.4 
+32.4 

+37.0 
-40.6 

+37.0 
+28.8 
-27.5 

+  13.9 
+21.6 

+10.8 
+  12.4 

+  16.8 
+21.4 
+22.1 

+3.7 

+5.7 

+6.9 
+7.6 

-9.7 
+  5.7 
+9.1 

+  8.4 
+11.7 

+  6.7 
-  8.0 

+  14.9 
+  4.7 
+  2.9 

-12.0 
+  10.9 

+  7.8 
+  6.6 

+  7.7 
+     .4 
+  4.0 

+30.5 
-  1.2 

+  9.1 
+  12.2 

+22.2 
+  19.4 
+26.1 

+30.6 
+33.1 

+36.2 
+22.8 

+  13.1 
+  9.7 
-14.0 

+75.1 
+81.8 

+77.5 
+53.6 

+65.0 
+61.3 
+50.2 

+61.2 

Heated ...            

+60.2 

Heated +5  per  cent  original 
soil 

+66.7 

Toluol 

+41.2 

Toluol+5  per  cent  original 
soil 

+48.2 

CS2 

+39.9 

CS2+5  per  cent  original  soil. . 

+28.1 

Soil  No.  486. 

Treatment. 

Days 

1-7. 

Days 

7-14. 

Days 
14-21. 

Days 
21-28. 

Days 
28-35. 

Davs 
35-94. 

Davs 
94-156. 

Davs 

7-156. 

Davs 
14-156. 

Check 

+  12.4 

+  72.8 

+64.0 
+69.4 

+  61.0 
+51.1 
+59.3 

+  7.6 
+24.0 

+  17.2 
+20.4 

+21.6 

+26.5 
+29.5 

+  5.0 

-  7.8 

+  3.7 
+  5.3 

+  13.2 
+  6.1 

-  4.6 

+  2.8 
-  8.8 

-18.1 
+  2.8 

-19.4 
+     .5 
+  11.2 

+  11.8 
+25.1 

+26.0 
+  13.2 

+  17.4 
+  5.6 
+  2.6 

+38.8 
-  3.4 

-26.7 
+23.4 
1     1.7 

+  11.9 

+68.1 

+  19.7 
+52.8 

+  17.8 
+  11.6 
+27.5 

+77.9 
+97.2 

+76.0 
+67.8 

+74.0 
+68.9 

+67.9 

+  70.3 

Heated 

+  73.2 

Heated+5  per  cent  original 

+58.8 

Toluol 

+47.4 

Toluol+5  per  cent  original 
soil 

+52.4 

CS2 

+42.4 

CS2+5 per  cent  original  soil. . 

+  38.4 

32 

Gain  (-f )  or  loss  (  — )  in  ammonia  and  nitrate  nitrogen  during  successive  periods — Contd, 


Treatment. 


Soil  No.  288. 


Days 
1-15. 


.Days 
15-33. 


Days 
33-82. 


Days 
15-82. 


Soil  No.  329.1 


Days 
1-15. 


Days      Days 
15-33.      33-80. 


Days 

15-80. 


Check 

Heated 

Heated+5  per  cent  original  soil 

Toluol  0.2  per  cent 

Toluol  4  per  cent 

Toluol  4  per  cent+5  per  cent  original 

soil 

CS2  0.2  per  cent 

CS2  4  per  cent 

CS2  4  per  cent+5  per  cent  original  soil 


+26.3 
+40.6 
+  9.1 

+20.4 


-1.4 
+  19.3 
+22.3 
+  19.5 


-  7.8 
+21.1 
+32.5 
+26.2 
+17.4 

+30.6 
+29.9 
+32.5 
+23.6 


+67.2 
+23.3 
+43.4 
+34.8 
+55.0 

+60.0 
+58.8 
+43.5 
+  12.0 


+59.4 
+44.4 
+75.9 
+61.0 

+72.4 

+90.6 
+88.7 
+76.0 
+35.6 


+  2.3 
-15.3 
-  7.8 
-47.2 
-10.0 

-14.1 
+48.6 
-21.4 
-21.9 


+74.3 
+78.3 
+72.4 
+89.6 
+56.2 

+67.1 
+20.4 
+50.4 

+54.3 


+45.8 
+90.2 
+54.8 
+87.6 
+55.2 

+31.8 
+37.0 
+33.4 
+35.0 


+  120.1 
+  168.5 
+  127.2 
+  177.2 
+  111.4 


57. 


1  Second  series. 

It  is  thus  shown  that  while  stimulation  in  ammonification  took 
place  in  practically  every  instance,  the  effects  were,  with  but  few 
exceptions,  of  short  duration,  generally  ceasing  after  about  15  days 
from  the  time  of  treatment.  Later  on,  the  time  varying  in  the  differ- 
ent soils  studied,  the  accumulation  of  available  nitrogen  became 
much  slower  in  the  partially  sterilized  soils,  with  the  result  that 
after  a  time  the  effects  of  the  treatment  disappeared  entirely. 


DISCUSSION. 

From  the  investigations  above  recorded  it  has  been  shown  that 
nitrification  does  not  take  place  in  most  Hawaiian  soils  unless  tillage 
is  employed,  and  that  the  effects  produced  by  aeration  may  be  soon 
destroyed  by  continued  wet  weather.  The  virgin  soils  will  not  sup- 
port nitrification  until  they  have  undergone  aeration  for  several 
months,  while  the  cultivated  soils  sustain  active  nitrification.  The 
lack  of  nitrification  in  the  former  is  not  due  to  the  absence  of  nitri- 
fying organisms  or  acidity.  Neither  will  the  mere  bringing  about  of 
aerobic  conditions  suffice.  It  is  necessary  that  oxidizing  conditions 
be  maintained  for  a  considerable  length  of  time  before  nitrification 
will  take  place.  Hawaiian  soils,  therefore,  require  the  operation  of 
the  weathering  process  in  order  to  become  suitable  to  the  activity  of 
nitrifying  bacteria. 

Some  of  the  inert  virgin  soils  appear  to  contain  soluble  substances 
which  inhibit  nitrification.  Sterilization  in  the  autoclave  affected 
both  cultivated  and  uncultivated  soil  in  such  way  as  to  render  them 
practically  equal  in  regard  to  subsequent  ammonification  and  brought 
about  conditions  toxic  to  nitrification  in  each  instance;  similar  effects 
were  produced  by  heating  to  still  higher  temperatures. 

Partial  sterilization  greatly  stimulated  ammonification,  which 
stimulation  persisted  usually  for  about  two  weeks  only,  followed  then 
by  a  retardation  in  ammonification  to  a  point  below  that  which  took 
place  in  the  untreated  soil. 


33 

Nitrification  was  prevented  for  a  short  time  by  partial  sterilization, 
but  later  regained  its  activity,  finally  becoming  more  active  than  in 
the  untreated  soil.  Partial  sterilization,  however,  did  not  bring 
about  conditions  in  the  inert  soils  as  favorable  to  nitrification  after 
reinoculation  as  are  produced  by  continued  aeration,  and  the  total 
available  nitrogen  found  in  the  partially  sterilized  soils  after  a  lapse 
of  several  months  was  in  a  number  of  instances  less  than  that  in  the 
untreated  soil. 

The  reinoculation  of  partially  sterilized  soils  with  5  per  cent  of  the 
original  soil  in  some  instances  caused  a  temporary  reduction  in  the 
amount  of  nitrate  and  ammonia  present,  but  this  effect  was  not 
always  permanent.  In  fact,  the  total  nitrate  and  ammonia,  in  the 
soils  kept  under  observation  for  the  greatest  length  of  time,  was  in 
some  instances  increased  by  reinoculation.  In  other  instances  no 
effects  were  produced,  while  in  still  other  instances  a  permanent 
reduction  in  the  amounts  of  available  nitrogen  was  brought  about. 

The  evidence  presented  above  seems  to  point  to  the  probability 
that  the  weathering  process,  aeration,  brings  about  effects  similar  in 
nature  but  differing  in  degree  from  those  produced  by  partial  sterili- 
zation. These  effects  are  believed  by  the  writer  to  be  in  part  of  the 
nature  of  oxidation,  but  more  largely  physical,  being  affected  through 
the  changes  produced  in  the  colloidal  soil  films. 

The  protozoan  theory  of  Russell  and  Hutchinson  appears  to  be  of 
doubtful  application  to  these  soils.  It  may  be  stated  that  some  of 
the  soils  studied,  especially  No.  428,  contained  numerous  organisms, 
apparently  infusoria  and  amoeba?,  so  numerous  indeed  as  to  be  easily 
detected  under  the  low-power  microscope.1  No  attempt  was  made 
to  identify  these  organisms,  but  they  appeared  to  be  as  numerous  in 
the  soil  treated  with  toluol  and  carbon  bisulphid  2  some  weeks  after 
treatment  as  in  the  untreated  soil.  In  the  heated  portions,  however, 
these  organisms  were  not  found,  but  ammonification  was  stimulated 
by  the  toluol  and  carbon  bisulphid  to  practically  the  same  extent  as 
by  heat. 

There  is  much  reason  for  the  belief  that  the  effects  produced  by 
different  methods  of  partial  sterilization  are  complicated  and  can 
not  be  satisfactorily  explained  as  being  due  to  a  simple  cause.  It 
has  been  repeatedly  shown  that  heating  to  98°  C.  causes  more  or 
less  decomposition  of  the  organic  matter  of  soils.  Such  changes 
certainly  affect  subsequent  bacterial  action.  Frequently  heat  has 
been  shown  to  bring  about  conditions  temporarily  toxic  to  the  nitri- 

1  Peck  has  previously  reported  the  presence  of  protozoa  in  Hawaiian  soils.  See  Hawaiian  Sugar  Planters, 
Sta.,  Agr.  and  Chem.  Bui.  34  (1910). 

2  Greig-Smith  found  that  the  addition  of  protozoa  to  cultures  did  not  reduce  the  numbers  of  bacteria 
during  70  days.  Likewise  the  addition  of  untreated  to  partially  sterilized  soil  produced  no  effects.  See 
Proc.  Linn.  Soc.  X.  S.  Wales,  37  (1912),  pp.  655-672. 


34 

fying  bacteria.  From  an  extensive  investigation  carried  out  in  this 
laboratory  it  was  shown  that  an  increase  in  the  solubility  of  the 
inorganic  constituents  takes  place  by  allowing  arable  soils  to  dry  out 
in  the  laboratory  1  and  that  a  considerably  greater  increase  in  solu- 
bility was  produced  by  heating  to  100°  C.  These  effects,  it  is  believed, 
are  due  to  alterations  in  the  colloidal  films  which  surround  soil  par- 
ticles and  which  seem  to  form  an  especially  important  feature  of 
Hawaiian  soils. 

Alterations  in  the  physical  nature  of  colloidal  films  may  reasonably 
be  believed  to  take  place,  as  a  result  of  drying  out  or  heating,  being 
brought  about  through  dehydration,  evaporation  from  the  interior 
to  the  exterior  of  the  film,  with  the  consequent  deposition  at  the 
surface  of  the  film  of  substances  held  in  solution,  and  changes  in  the 
physical  nature  of  the  colloids.  Such  effects  may  be  conceived  to 
be  of  considerable  biological  significance,  for  new  points  of  attack 
would  thus  become  exposed,  fresh  supplies  of  organic  material  pre- 
viously more  or  less  protected  from  bacterial  invasion  would  be  laid 
open,  and  an  increased  food  supply  brought  within  their  easy  reach. 

In  addition  bacteriotoxins,  if  present,  would  probably  undergo 
some  decomposition,  and  the  organisms  surviving  the  heat  would 
find  in  the  cells  of  the  organisms  killed  an  additional  store  of  material 
perhaps  easily  susceptible  to  decomposition. 

The  action  of  volatile  antiseptics  may  be  explained  on  very  similar 
grounds,  the  effects  produced  in  this  case  being  on  soil  films,  but 
brought  about  through  solvent  effects,  after  the  manner  described  by 
Greig-Smith.2  That  there  are  substances  in  soils  soluble  in  toluol, 
carbon  bisulphid,  chloroform,3  etc.,  can  hardly  be  doubted  and  that 
such  substances  would  tend  to  accumulate  around  soil  particles  in 
and  on  the  films  also  seems  very  probable.  The  volatile  antiseptics 
would  dissolve  some  of  this  material,  although  the  amounts  employed 
be  small  and  upon  evaporation  a  redistribution  of  the  dissolved  sub- 
stances would  be  expected.  Thus  new  surfaces  of  organic  matter 
previously  protected  in  part  against  bacterial  invasion  would  become 
exposed.  It  seems  probable,  moreover,  that  some  direct  stimula- 
tion would  result  to  the  surviving  organisms. 

Thus,  according  to  this  view,  the  effects  produced  by  partial 
sterilization  are  explainable  largely  on  the  basis  of  its  making  avail- 
able to  the  surviving  organisms  food  and  organic  materials  through 
alterations  in  the  colloidal  films.  The  effects  produced  by  aeration 
are  probably  in  considerable  part  of  the  same  nature  with  the  addi- 

i  Hawaii  Sta.  Bui.  30  (1913). 

2  Froc.  Linn.  Soc.  N.  S.  Wales,  35  (1910),  pp.  808-822B;  36  (1911),  pp.  609-612,  679-699;  37  (1912),  pp.  238- 
243,  655-S72. 
»  Texas  Sta.  Bui.  155  (1913). 


35 

tion  of  granulation  effects  and  oxidative  *  decompositions,  the  latter 
of  which  are  probably  of  special  importance  to  the  nitrifying  organisms. 
In  these  investigations  only  one  of  the  different  methods  employed 
in  soil  bacteriology,  namely,  that  of  measuring  the  products  formed, 
has  been  employed.  There  is  urgent  necessity  for  further  work  on 
this  subject  before  the  fundamental  principles  can  be  positively 
established. 

THE    LIME-MAGNESIA   RATIO. 

As  stated  in  the  introduction,  lime  and  magnesia  occur  in  Hawaiian 
soils  in  widely  variable  amounts,  both  relatively  and  absolutely, 
but  generally  speaking  the  magnesia  content  exceeds  that  of  lime. 
The  lime-magnesia  ratio  therefore  is  abnormal.  For  a  number  of 
years  an  increasing  interest  has  been  taken  in  this  ratio  in  its  rela- 
tions to  plant  growth.  Widely  different  conclusions  have  been 
reached. 

The  subject  received  one  of  its  first  important  contributions  from 
the  work  of  Loew  and  May  2  in  1901.  As  a  result  of  their  experi- 
ments they  concluded  that  the  ratio  of  lime  to  magnesia  has  an 
important  bearing  upon  the  growth  of  crops.  During  the  following 
years  Loew  and  his  coworkers  in  Japan  3  conducted  further  experi- 
ments along  this  line  both  in  culture  solutions  and  soil  cultures, 
which  further  confirmed  the  conclusion  arrived  at  formerly.  As 
a  result,  the  lime-magnesia  ratio  in  soils  has  come  to  be  known  as 
the  Loew  theory.  In  general  Loew  found  that  a  number  of  plants 
were  considerably  affected  by  variations  in  this  ratio  and  that  different 
ratios  are  best  suited  to  the  growth  of  different  species. 

Other  investigators,4  working  with  both  field  and  pot  cultures, 
have  arrived  at  altogether  different  conclusions,  while  Voelcker,5  after 
several  years  of  careful  pot  experimentation,  confirmed  the  theory 
so  far  as  the  growth  of  wheat  was  concerned. 

From  water  cultures  conducted  at  the  Porto  Rico  Station,  Gile  6 
found  that  the  concentration  is  of  the  greatest  importance  in  deter- 
mining whether  the  ratio  of  lime  to  magnesia  exerts  an  influence  on 
growth.  At  a  low  concentration  he  found  that  a  wide  variation  in 
this  ratio,  10:1  to  1:10,  exerted  no  influence,  while  at  a  much  higher 
concentration  the  ratio  is  of  considerable  significance.  He  con- 
cluded, however,  that  the  higher  concentration  is  rarely  found  in 

1  The  presence  of  ferrous  iron  compounds  suggests  itself  as  being  related  to  the  inactive  state  of  nit.  'n- 
cation  in  the  uncultivated  soils.     Hawaiian  soils  contain  unusually  large  amounts  of  iron,  a  considerable 
portion  of  which  exists  as  ferrous  oxid,  but  the  water  soluble  ferrous  iron  occurs  in  extremely  small 
amounts.    The  difference  between  the  cultivated  and  uncultivated  soils  in  this  respect  is  very  slight.    See " 
Hawaii  Sta.  Bui.  30. 

2  U.  S.  Dept.  Agr..  Bur.  Plant  Indus.  Bui.  1. 

3  Aso,  Bui.  Col.  Agr.,  Tokyo  Imp.  Univ.,  4  (1902),  pp.  361-370;  5  (1903),  pp.  495-499;  6  (1904),  pp.  97-102; 
Loew  and  Aso,  ibid.,  7  (1907),  pp.  395-409. 

«  Lemmermann  et  al.,  Landw.  Jahrb.,  40  (1911),  pp.  173-254. 
'•>  Jour.  Roy.  Agr.  Soc.  England,  73  (1912),  pp.  325-338. 
e  Porto  Rico  Sta.  Bui.  12  (1913). 


36 

soil  solutions  and  therefore  variations  in  this  ratio  in  natural  soils 
would  rarely  be  consequential  to  crops. 

Concerning  the  correctness  of  this  conclusion  opinions  may  well 
differ,  since  the  concentration  of  the  real  soil  solution,  the  film 
moisture,  is  not  and  can  hardly  be  known  in  the  present  state  of 
knowledge.  The  principle  under  consideration  must  of  necessity 
be  worked  out  from  culture  solutions  or  sand  cultures,  since  in  such 
a  complex  as  an  ordinary  soil  the  number  of  variables  are  entirely 
too  numerous  to  permit  the  establishing  of  the  principle  with  definite- 
ness. 

From  what  is  known  regarding  the  different  phases  of  the  osmotic 
phenomenon  in  their  bearings  on  the  absorption  of  chemical  substances 
by  plant  roots,  it  can  hardly  be  doubted  that  any  considerable  varia- 
tion in  the  concentration  of  such  elements  as  calcium  and  magnesium 
in  nutrient  solutions  is  likely  to  be  attended  by  physiological  effects, 
especially  in  certain  plants. 

On  the  other  hand,  the  effects  produced  on  concentration  by  the 
application  of  the  comparatively  small  amounts  of  lime  and  magnesia 
usually  employed  in  field  experiments  can  only  be  surmised.  The 
mere  application  of  a  given  amount  of  soluble  calcium  or  magnesium 
by  no  means  insures  a  corresponding  increase  in  the  concentration 
of  these  elements  in  the  soil  solution.  Therefore  that  widely  different 
results  have  been  obtained  in  studies  with  soils  of  different  origin, 
composition,  and  properties  is  not  surprising. 

Concerning  the  biological  phases  of  this  question  a  few  experiments 
have  been  conducted. 

In  1904  Lohnis  x  found  that  the  addition  of  magnesium  carbonate 
to  culture  solutions  caused  a  loss  of  ammonia  from  the  solutions, 
from  which  he  concluded  that  this  substance  is  unsuited  to  use  in 
nitrification  studies'.  In  1907  Lipman  and  Brown  2  found  that  the 
addition  of  magnesium  carbonate  to  Omelianski  solutions  caused 
a  loss  of  ammonia  during  sterilization,  and  that  upon  subsequent 
inoculation  with  a  soil  infusion  still  greater  losses  occurred,  amount- 
ing in  25  days  to  more  than  50  per  cent  of  the  ammonia  originally 
present.  Small  losses  of  ammonia  were  also  sustained  where  calcium 
carbonate  was  used.  In  addition  only  slight  nitrification  took  place 
in  the  solutions  which  contained  magnesium  carbonate,  reaching 
a  maximum  by  the  sixth  day  followed  by  denitrification,  whereas 
active  nitrification  took  place  throughout  the  25-day  period  of  obser- 
vation where  calcium  carbonate  was  used.  On  the  other  hand,  Owen 3 
in  1908  concluded  that  magnesium  carbonate  is  better  suited  to  the 
stimulation  of  nitrification  thau  calcium,  potassium,  or  ammonium 
carbonates. 

i  Centbl.  Bakt.[etc],  2.  Abt.,  13  (1904),  pp.  706-715. 

2  Jour.  Amer.  Chem.  Soc,  29  (1907),  pp.  1358-1362. 

3  Georgia  Sta.  Bui.  81  (1908). 


37 

In  1907  Ashby  '  found  that  in  the  presence  of  magnesium  carbonate, 
Azotobacter  from  the  Rothamsted  experimental  plats  fixed  more 
nitrogen  in  mannite  solutions,  both  in  pure  and  mixed  cultures, 
than  in  the  presence  of  calcium  carbonate.  A  mixture  of  the  two 
carbonates  proved  more  effective  than  calcium  carbonate  alone. 
The  author  concluded  "that  magnesium  carbonate  not  only  neutral- 
izes more  effectually  than  calcium  carbonate  any  trace  of  acidity 
due  to  foreign  organisms  in  the  early  stages  of  culture,  but  also 
prevents  butyric  fermentation,  but  at  first  it  inhibits  the  growth  of 
Azotobacter  itself."  In  further  investigation  2  he  found  that  mag- 
nesium carbonate  caused  a  greater  loss  of  ammonia  from  ammonium 
sulphate  solution  than  calcium  carbonate.  This  loss  Ashby  attributed 
to  the  interaction  between  ammonium  sulphate  and  the  carbonates, 
whereby  ammonium  carbonate  is  formed,  which  in  turn  tends  to 
volatilize  from  the  solutions.  Magnesium  carbonate  being  more 
soluble  than  calcium  carbonate,  would,  therefore,  give  rise  to  greater 
amounts  of  ammonium  carbonate,  for  which  reason  he  accounts  for 
the  greater  losses  in  the  former  instances. 

C.  B.  Lipman  3  found  that,  in  the  presence  of  more  than  very  low 
concentrations  of  magnesium  chlorid,  the  ammonification  of  peptone 
by  Bacillus  subtilis  was  greatly  hindered,  and  that  the  simultaneous 
addition  of  varying  amounts  of  calcium  chlorid  did  not  overcome 
the  toxic  effects.  He  concluded,  therefore,  that  magnesium  chlorid 
is  toxic  to  the  action  of  B.  subtilis,  and  that  there  is  no  antagonism 
between  calcium  and  magnesium  chlorids  so  far  as  the  ammonifica- 
tion of  peptone  is  concerned.  It  should  be  borne  in  mind,  however, 
that  in  general  it  has  been  found  that  calcium  is  not  necessary  to 
the  growth  of  bacteria,  and  therefore,  from  the  conception  under- 
lying Loew's  theory,  there  need  not  be  any  antagonism  between 
calcium  and  magnesium.  The  point  of  greatest  interest  in  Lipman's 
experiments  in  this  connection,  however,  is  the  fact  that  the  mag- 
nesium salt  actually  proved  toxic  at  low  concentration. 

In  1908  Fraps  4  found  from  some  investigations  with  soils  in  Texas 
that  the  addition  of  calcium  carbonate  caused  a  greater  stimulation 
to  the  nitrification  of  cottonseed  meal  than  magnesium  carbonate, 
and  that  a  mixture  of  the  two  produced  intermediate  effects. 

J.  G.  Lipman,  P.  E.  Brown,  and  I.  L.  Owen5  observed  in  1910  that 
the  addition  of  1  gram  of  calcium  carbonate  per  100  grams  of  a  soil 
from  New  Jersey  caused  a  stimulation  in  the  ammonification  of 
dried  blood,  but  hindered  the  ammonification  of  cottonseed  meal. 
On  the  other  hand,  magnesium  carbonate  was  toxic  to  the  ammoni- 

1  Jour.  Agr.  Sci.,  2  (1907),  pp.  35-51. 

2  Idem,  pp.  52-67. 

•  Bot.  Gaz.,  48  (1909),  pp.  105-125;  49  (1910),  pp.  41-50. 

*  Texas  Sta.  Bui.  106  (1908). 

&  New  Jersey  Stas.  Rpt.  1910,  p.  114. 


38 

fication  of  dried  blood,  but  stimulated  the  ammonification  of  cotton- 
seed meal.  In  the  same  year,  Kellerman  and  Kobinson 1  found 
that  the  addition  of  magnesium  carbonate  to  a  magnesian  soil  in 
quantities  greater  than  0.25  per  cent  depressed  the  formation  of 
nitrates,  while  calcium  carbonate  exerted  a  stimulating  effect. 

In  investigations  carried  out  in  India  in  1910  and  1911,  C.  M. 
Hutchinson  2  found  that  the  addition  of  magnesium  carbonate  to 
full  strength  Omelianski  solutions  caused  considerable  loss  of  ammonia 
but  only  slight  losses  from  dilute  solutions.  Furthermore,  neither 
the  neutralization  of  the  magnesium  carbonate  with  sulphuric  acid 
nor  the  synchronous  addition  of  calcium  carbonate  overcame  the 
loss.  In  nitrification  experiments  Hutchinson  found  that  the  addi- 
tion of  magnesium  carbonate  to  dilute  solutions  partially  prevented 
nitrate  formation  for  a  few  weeks,  but  at  the  end  of  12  weeks  the 
toxic  effects  had  disappeared.  With  full-strength  solutions,  nitri- 
fication was  greatly  reduced  by  magnesium  carbonate,  and  again  the 
toxic  effects  were  not  overcome  by  neutralizing  the  magnesium 
carbonate.  Calcium  carbonate,  on  the  other  hand,  did  not  interfere 
with  nitrification. 

In  1912  the  writer3  conducted  a  series  of  experiments  on  "this 
subject,  using  two  sandy  soils  from  California.  In  the  ammonifi- 
cation of  dried  blood  85  milUgrams  of  ammonia  nitrogen  were  formed 
with  calcium  carbonate  and  only  53.9  milligrams  with  magnesium 
carbonate,  and  no  antagonism  was  found  between  the  two  carbonates. 
In  nitrification  studies  using  dried  blood,  calcium  carbonate  produced 
about  50  per  cent  stimulation,  but  magnesium  carbonate  totally 
inhibited  nitrification.  In  addition  to  preventing  nitrification, 
magnesium  carbonate  also  caused  slight  denitrification,  the  original 
nitrate  content  having  been  reduced  from  5  milligrams  per  100  to  2 
milligrams,  where  2  grams  of  magnesium  carbonate  was  added,  and 
finally  no  antagonism  was  found  between  calcium  and  magnesium 
carbonates. 

In  view  of  the  results  previously  found  and  the  fact  that,  in  the 
main,  conditions  differing  greatly  from  those  encountered  in  field 
studies  have  been  employed,  it  becomes  important  to  study  the 
question  further.  It  is  of  special  importance  to  study  the  effects  of 
different  ratios  of  lime  and  magnesia  on  the  various  phases  of  bacterial 
action  in  soils,  since  it  is  now  recognized  that  so  much  depends  upon 
the  biological  phenomena  of  soils.  The  following  investigation  is 
offered  as  a  contribution  to  the  ammonification  and  nitrification 
phases  of  this  question. 

1  Science,  n.  ser.,  32  (1910),  p.  159. 

2  Mem.  Dept.  Agr.  India,  Bact.  Ser.,  1  (1912),  No.  1. 
»  Univ.  Cal.  Pubs.  Agr.  Sci.,  1  (1912),  pp.  39-49. 


39 


EFFECTS    OF    CALCIUM    AND    MAGNESIUM    CARBONATES    ON 
AMMONIFICATION. 

In  experiments  on  this  subject  100-gram  portions  of  air-dried  soils, 
selected  so  as  to  represent  the  principal  types  found  in  Hawaii,  were 
thoroughly  mixed  with  2  grams  of  the  nitrogenous  materials  and 
carbonates,  then  placed  in  tumblers,  brought  to  optimum  moisture, 
and  covered  with  watch  glasses.  Dried  blood  was  used  as  a  source 
of  nitrogen.  After  incubation  for  seven  days,  at  from  27°  to  29°  C, 
the  ammonia  was  determined  by  distillation  in  the  usual  way. 

The  soils  used  varied  greatly  in  physical  and  chemical  composition. 
No.  288  is  a  heavy  ferruginous  clay  soil,  containing  1.10  per  cent 
lime  and  7.94  per  cent  magnesia.  No.  330  is  a  heavy  clay  soil  from 
the  pineapple  section  of  the  Wahiawa  district.  This  sample  con- 
tained less  than  0.2  per  cent  of  both  lime  and  magnesia.  No.  335  is 
coral  sand  soil  already  described.  The  results  are  shown  in  the 
following  table: 

Effects  of  calcium  and  magnesium  carbonates  on  the  ammonification  of  dried  blood. 

[Milligrams  of  ammonia  nitrogen  per  100  grams  soil.] 


Soil 
por- 
tions. 


Carbonate  added. 


Soil  No.  288. 


Dupli-        Aver- 
cates. 


Soil  No.  330. 


Dupli-       Aver- 
cates. 


Soil  No.  335. 


Dupli-       Aver- 
cates. 


None.. 
0.1  gm. 
0.1  gm. 
0.5  gm. 
0.5  gm. 
1.0  gm. 
1.0  gm. 
2.0  gm. 
2.0  gm. 
4.0  gm. 
4.0  gm. 
8.0  gm. 
8.0  gm. 
0.1  gm. 
0.1  gm. 
0.5  gm. 

18  0.5  gm. 

19  1.0  gm. 
1.0  gm. 
2.0  gm. 
2.0  gm. 
4.0  gm. 
4.0  gm. 
8.0  gm. 
8.0  gm. 


CaC03.. 
CaC03.. 
CaC03. 
CaC03.. 
CaC03. . 
CaC03. 
CaCOs. 
CaC03. 
CaCOs. 
CaCOs. 
CaCOs. 
CaCOs. 
MgC03. 
MgC03. 
MgC03. 
MgC03. 
MgC03. 
MgC03. 
MgC03. 
MgC03. 
MgC03. 
MgC03. 
MgC03. 
MgC03. 


77. 

93. 

77. 

85. 

95. 

91. 

87. 
C1) 

95. 

57. 

59. 

87. 

94. 

78. 

94. 
100. 

82. 

99. 
C1) 

90. 

98. 

84. 

68. 

64. 

64. 


68.4 
"85.'6" 

90."  6' 
'89.*5' 
'95.'6' 
'58."5* 
'91.Y 


83. 
63. 
62. 
65. 

C1) 


73.6 


99.3 
93.8 


96.5 


64.1 


91.0 
«.*7 


94.2 
"76."  3 
'64."2 


83. 

57. 

88. 

84. 
108. 
105. 
123. 

51. 

79. 

49. 

65. 
112. 
121. 
125. 
125. 
108. 
113. 


99.4 


89.0 
'7L5" 
*72.'6" 

96.' 4' 

iii.'i" 

'65.' 6' 
*S7."8 
il6*9" 
i25."4" 

iii.'-i' 

"94.'6 


57.3 

64.7 
54.0 
54.2 
54.0 
56.8 
49.6 
52.4 


62.0 


54.1 
'55."4 

si.6 


iLost. 

The  above  results  show  a  wide  difference  in  the  effects  produced 
in  the  different  soils.  In  soil  No.  288  the  addition  of  calcium  car- 
bonate up  to  2  per  cent  caused  a  gradational  increase  in  ammonia 
formation,  but  with  larger  amounts  slightly  less  ammonia  was  found. 
With  soil  No.  330,  calcium  carbonate  in  amounts  less  than  4  per  cent 
produced  only  slight  effects,  while  the  larger  amounts  stimulated 
ammonification.  These  effects  may  be  due  to  physical  causes,  since 
these  soils  are  extremely  heavy  and  the  addition  of  the  larger  amounts 


40 


of  calcium  carbonate  probably  exerted  an  effect  upon  the  texture 
so  as  to  permit  better  aeration. 

Magnesium  carbonate  *  produced  effects  in  soil  No.  288  similar  to 
those  produced  by  calcium  carbonate.  But  in  soil  No.  330,  a  reduc- 
tion in  the  amounts  of  ammonia  formed  was  caused  by  the  smaller 
amounts  of  magnesium  carbonates,  while  the  larger  amounts  caused 
considerable  stimulation.  In  soil  No.  335,  magnesium  carbonate 
markedly  decreased  the  amounts  of  ammonia  that  accumulated. 

EFFECTS  OF  CALCIUM  AND  MAGNESIUM  CARBONATES  ON  THE 
AMMONIFICATION  OF  DRIED  BLOOD  AND  SOY  BEAN  CAKE 
MEAL. 

Two  different  nitrogenous  substances  were  employed,  dried  blood 
and  soy  bean  cake  meal,  the  latter  of  which  represents  the  residue 
left  after  expressing  the  oil  from  the  soy  bean,  and  is  produced  in 
certain  parts  of  the  Orient  in  enormous  quantities,  where  it  is  used 
both  as  a  feed  and  a  fertilizer.  The  dried  blood  used  contained  13.29 
per  cent  nitrogen,  the  soy  bean  cake  meal  8.28  per  cent.  Of  the  soils 
employed,  No.  9  is  highly  manganiferous  and  silty  in  character;  No. 
292  is  a  gravelly  loam  of  unusually  high  magnesium  content;  No. 
428  contains  a  large  amount  of  organic  matter  and  considerable 
amounts  of  calcium  carbonate;  No.  448  is  a  yellow  clay  soil,  taken 
from  the  grounds  of  the  Hilo  Boarding  School;  No.  461  is  clay  loam 
taken  from  the  rice  lands  of  the  Hanalei  Valley.  The  other  soils 
studied  have  already  been  discussed.  After  mixing  with  the  organic 
nitrogenous  materials  and  carbonates,  bringing  to  optimum  moisture, 
and  incubation  for  seven  days,  the  ammonia  was  determined  as  usual. 
The  results  are  shown  in  the  following  table : 

Effects  of  calcium  and  magnesium  carbonates  on  the  ammonification  of  dried  blood  and 

soy  bean  cake  meal. 


[Average  amount 

in  milligrams  of  ammonia  nitrogen  formed  per  100  grams  of  soil.] 

Carbonate 

Soil  No.  9. 

Soil  No. 
292. 

Soil  No. 
428. 

Soil  No. 

448. 

Soil  No. 
461. 

Soil  No. 
485. 

Soil  No. 
487. 

Soil 

d 

a 

d 

a 

d 

fl 

-d 

a 

d 

a 

d 

a 

d 

a 

por- 
tions. 

added. 

8 

Jo 

o3 

*j8 

o 
2 

2 

03 

8 
fit 

03 
®  ^ 

^3 

§ 

fi 

03 

| 

03 

^3 

o 
o 

2 

03 
^3 

*g 

T3 
flj 

^ 

t3 

.2 

'    e3 

1 

*S 

.1 

*8 

^g 

.1 

•    03 

"«H 

o 

o 

O 

n 

o 

U 

o 

O 

t-> 

o 

A 

co 

A 

co 

A 

CO 

A 

CO 

A 

GO 

A 

CO 

A 

CO 

1,2... 

None 

51.9 

99.1 

156.9 

94.1 

53.4 

74.3 

39.3 

78.1 

94.4 

98.3 

45.9 

79.9 

31.0 

77.0 

3,4... 

l.Ogm.  CaC03-- 

54.4 

103.7 

160.3 

97.2 

52.6 

79.5 

42.0 

80.0 

118.1 

93.1 

27.2 

83.2 

5,6... 

2.0gm.CaCO3... 

55.4 

104.8 

158. 9 

99.5 

64.4 

82.4 

42.7 

82.5 

126.2 

93.2 

'46.'  7 

'90."  6 

30.8 

87.0 

7,8... 

4.0gm.CaCO3... 

56.1 

103.4 

160.1 

96.8 

61.3 

88.9 

44.3 

88.9 

116.6 

95.4 

31.3 

84.2 

9,10.. 

l.Ogm.MgCOs-. 

68.0 

104.1 

175.0 

93.9 

68.6 

78.5 

53.6 

95.1 

119.8 

94.5 

42.1 

83.6 

11,12. 

2.0gm.MgCO3.. 

70.9 

103.6 

163.8 

95.0 

93.6 

82.7 

67.6 

98.8 

89.6 

94.1 

"60."  7 

'91.'  7 

50.0 

85.7 

13,14. 

4.0  gm.  MgC03.. 

65.9 

98.7 

172.0 

92.3 

109.9 

92.5 

73.5 

100.8 

82.8 

89.9 

38.3 

80.7 

15, 16. 

2.0  gm.  CaC03+ 

2  gm.  MgC03. 

4.0  gm.CaC03+ 

69.8 

101.3 

90.7 

86.8 

68.9 

97.3 

1C2.6 

91.3 

6i.6 

"9i."6 

46.5 

90.9 

17, 18. 

70.9 

104.8 

92.4 

98.7 

83.4 

67.6 

95.9 

99.7 

92.4 

62.2 

97.7 

52.4 

91.1 

2  gm.  MgC03. 

1  Baker's  analyzed  magnesium  carbonate,  having  the  composition,  3MgC03.Mg(0H)23  H20,  was  used 
in  these  experiments.  In  all  other  instances  reported  in  this  bulletin  Merck's  reagent  magnesium 
carbonate,  MgC03,  was  used. 


41 

Considering  first  the  calcium  carbonate,  it  will  be  seen  that  only 
slight  effects  were  produced  on  the  ammonification  of  either  dried 
blood  or  soy  bean  cake  meal  in  soils  Nos.  9,  292,  428,  448,  and  487, 
and  on  the  ammonification  of  soy-bean  cake  in  No.  461  and  that  of 
dried  blood  in  No.  485,  while  considerable  stimulation  resulted  in 
the  ammonification  of  dried  blood  in  No.  461  and  of  soy-bean  cake 
in  No.  485.  With  the  addition  of  magnesium  carbonate,  the  am- 
monification of  dried  blood  was  stimulated  in  every  soil  except  No. 
461,  as  also  was  the  ammonification  of  soy  bean  cake  meal  in  Nos. 
428,  448,  and  485.  On  the  other  hand,  magnesium  carbonate  produced 
no  effects  on  the  ammonification  of  soy-bean  cake  in  soils  Nos.  9, 
292,  and  461.  In  one  case  only — dried  blood  in  soil  No.  461 — the 
addition  of  magnesium  carbonate  caused  a  decrease  in  the  amounts 
of  ammonia  found. 

In  those  instances  where  magnesium  carbonates  produced  stimu- 
lation the  further  addition  of  calcium  carbonate  was  without  effect 
on  this  stimulation.  In  the  one  instance  where  magnesium  carbo- 
nate proved  toxic  the  addition  of  calcium  carbonate,  however, 
seems  to  have  overcome  the  toxicity.  It  is  doubtful,  however, 
whether  this  is  a  true  case  of  antagonism,  so  far  as  the  biological 
processes  are  concerned. 

The  effects  produced  by  magnesium  carbonate  in  Hawaiian  soils, 
therefore,  proved  to  be  quite  opposite  to  those  found  in  ammonifi- 
cation studies  in  solutions  and  in  the  few  soils  previously  reported. 
The  majority  of  soils  used  above  contained  an  excess  of  magnesia 
over  lime — No.  292  especially  so — yet  we  find  that  the  addition  of 
calcium  carbonate  produced  only  slight  stimulation,  whereas  the 
addition  of  magnesium  carbonate  usually  caused  considerable  stim- 
ulation. It  seems  justifiable  to  conclude,  therefore,  that  the  lime- 
magnesia  ratio  as  such  has  but  little  or  no  significance  to  the  ammoni- 
fication process.  Tlje  above  results,  moreover,  are  in  harmony  with 
the  observations  of  Lipman  et  al.  in  that  the  effects  produced  by 
magnesium  carbonate  depend  in  some  instances  on  the  nitrogenous 
material  being  acted  upon;  and,  finally,  it  is  of  interest  that  mag- 
nesium carbonate  caused  a  more  marked  stimulation  of  the  ammoni- 
fication of  dried  blood  than  of  soy  bean  cake  meal'. 

The  inference  has  already  been  made  that  the  smaller  amounts 
of  ammonia  found  where  magnesium  carbonate  was  added  are  due 
to  the  formation  of  ammonium  carbonate  and  its  volatilization 
rather  than  to  an  actual  inhibition  of  the  ammonification  process. 
In  order  to  throw  some  light  on  this  point,  further  experiments 
were  carried  out  with  soil  No.  335.  In  these  experiments  100-gram 
portions  were  mixed  with  the  carbonates  and  dried  blood,  then 
brought  to  optimum  moisture  by  the  addition  of  sterile  water,  and 
placed  in  wide-mouthed  bottles  fitted  with  two-hole  rubber  stoppers, 


, 


42 

through  which  a  slow  current  of  air  was  slowly  drawn  by  means  of 
a  filter  pump.  The  air  was  first  drawn  through  a  solution  of  sul- 
phuric acid  in  order  to  free  it  from  all  traces  of  ammonia,  then  after 
passing  over  the  soil  in  the  bottles  was  again  drawn  through  sul- 
phuric acid.  After  seven  days'  incubation  the  ammonia  was  deter- 
mined, both  in  the  soil  and  in  the  sulphuric  acid.  The  results  are 
shown  in  the  following  table : 

Ammonification  of  dried  blood,  showing  total  ammonia  formed. 


Son 

por- 
tions. 


Carbonate  added. 


Soil  335. 


Ammonia 

nitrogen 

found. 


Ammonia 
nitrogen 
vola- 
tilized. 


Totals. 


Averages. 


1 
2 

3 
4 


2  gm.  CaC03. 
2  gm.  CaC03. 
2  gm.  MgCOs 
2  gm.  MgC03 


Mg. 
56,7 
67.3 
38.5 
40.5 


Mg. 
17.4 
10.9 
17.2 
22.4 


Mg. 
74.1 
78.2 
55.7 
62.9 


Mg. 


76.1 
'59."3 


The  above  data  show  that  14.1  milligrams  of  ammonia  nitrogen 
was  volatilized  under  the  influence  of  calcium  carbonate  and  19.8 
milligrams  with  magnesium  carbonate.  On  the  other  hand,  62 
milligrams  accumulated  in  the  soil  where  calcium  carbonate  was 
added  and  only  39.5  milligrams  with  magnesium  carbonate.  Com- 
bining the  ammonia  accumulated  and  that  volatilized,  we  find 
that  76.1  milligrams  of  nitrogen  was  ammonified  in  the  presence  of 
calcium  carbonate  and  only  59.3  milligrams  in  the  presence  of 
magnesium  carbonate.  It  is  thus  shown  that  in  this  soil  magne- 
sium carbonate  was  actually  toxic  to  ammonification.  It  will 
be  recalled  that  the  soil  used  is  composed  principally  of  grains  of 
coral  sand  (CaC03),  yet  the  addition  of  relatively  small  amounts 
of  magnesium  carbonate  proved  toxic.  The  conclusion,  therefore, 
seems  justifiable  that  magnesium  carbonate  is  toxic  to  the  ammoni- 
fying flora  of  this  soil,  although  there  are  other  factors  that  must  be 
considered. 

EFFECTS  OF  NATURAL  LIMESTONES  ON  AMMONIFICATION. 

Notwithstanding  the  theoretical  interest  attached  to  the  effects 
produced  by  magnesium  carbonate,  it  is  of  more  practical  value 
to  determine  the  effects  produced  by  the  naturally  occurring  double 
carbonate  of  magnesium  and  calcium  [MgCa(COs)2],  dolomite,  which 
is  present  in  greater  or  lesser  amounts  in  practically  all  limestones 
which  are  now  being  applied  to  soils.  Through  the  kindness  of 
A.  F.  Whiting,  of  the  University  of  Illinois,  a  few  pounds  of  pulver- 
ized limestone  (CaC03)  and  a  very  pure  dolomite  were  obtained,  each 
of  which  is  reported  as  being  used  on  a  large  scale. 


4S 


In  order  to  study  the  effects  produced  by  these  materials,  both 
as  regards  stimulation  and  toxicity,  three  of  the  soils  previously 
studied  were  employed,  using  also  chemically  pure  carbonates, 
both  singly  and  combined,  in  amounts  corresponding  to  those  in 
which  the  carbonates  occur  in  dolomite.  The  results  are  shown 
in  the  following  table : 

Ammonijication,  showing  effects  produced  by  natural  limestones. 
[Average  amount  in  milligrams  of  ammonia  nitrogen  per  100  grams  soil.] 


Soil 
por- 
tions. 


Carbonate  added. 


Soil  No.  335. 


Dried 
blood. 


Soy-bean 
cake. 


Soil 
No.  465. 


Dried 
blood. 


Soil 
No.  516. 


Dried 
blood. 


1,2.. 

3,4.. 
5,6.. 
7,8.. 
9,10. 
11,12 


None 

2  gm.  CaC03 

2gm.MgC03 

1.1  gm.  CaCO3+0.9  gm.  MgC03 

2  gm.  limestone  (CaCOs) 

2  gm.  dolomite 


50.2 
54.2 
30.2 
29.9 
50.5 


55.7 
53.7 
46.4 
46.9 
56.7 
55.4 


102.2 
110.6 
114.1 
121.6 
108.9 
104.6 


92.7 
99.7 
116.1 
109.8 
94.5 
92.2 


Again,  it  is  shown  that  calcium  carbonate  produced  only  slight 
stimulation  in  the  ammonification  of  dried  blood  and  was  without 
effect  on  that  of  soy  bean  cake  meal.  Magnesium  carbonate,  on 
the  other  hand,  was  toxic  to  the  ammonification  of  dried  blood  in 
soil  No.  335  but  stimulating  in  the  other  soils.  The  effects  pro- 
duced by  addition  of  the  two  carbonates  were  similar  to  those  pro- 
duced by  magnesium  carbonate  alone.  Where  the  natural  lime- 
stones were  added,  on  the  other  hand,  it  will  be  seen  that  both  the 
calcareous  and  the  dolomitic  limestones  produced  effects  very 
similar  to  those  produced  by  calcium  carbonate.  Dolomite  neither 
proved  toxic  in  soil  No.  335  nor  stimulating  in  soils  Nos.  465  and  516. 
Thus  it  is  shown  that  the  effects  produced  by  dolomite  in  no  way  simu- 
lated those  produced  by  magnesium  carbonate.  Further  discussion 
on  this  point  will  be  made  after  the  results  from  the  nitrification 
studies  have  been  presented. 

EFFECTS  OF  CALCIUM  AND  MAGNESIUM  CARBONATES  ON 
NITRIFICATION. 

In  the  nitrification  experiments,  100-gram  portions  of  air-dried 
soils,  after  thoroughly  mixing  with  the  nitrogenous  materials  and 
carbonates,  were  kept  at  optimum  moisture  in  tumblers  for  21  days, 
after  which  the  nitrates  were  determined  by  the  phenol-disulphonic 
acid  method.  Dried  blood  and  soy  bean  cake  meal  were  added 
at  the  rate  of  2  grams  per  100  grams  of  soil,  and  ammonium  sul- 
phate at  the  rate  of  1.2  grams,  which  furnished  nitrogen  in  an  amount 
intermediate  between  those  supplied  by  the  dried  blood  and  soy 
bean  cake  meal. 


44 


Effects  of  calcium  and  magnesium  carbonates  on  nitrification. 

[Milligrams  of  nitrate  nitrogen  per  100  grams  soil.] 

DRIED  BLOOD,  2  GRAMS. 


Soil 
por- 
tions. 

Carbonate  added. 

Soil  No.  292. 

Soil  No.  288. 

Soil  No.  329. 

Soil  No.  428. 

Soil  No.  448. 

Soil  No.  485. 

Du- 
pli- 
cates. 

Av- 
er- 
ages. 

Du- 
pli- 
cates. 

Av- 
er- 
ages. 

Du- 
pli- 
cates. 

Av- 
er- 
ages. 

Du- 
pli- 
cates. 

Av- 
er- 
ages. 

Du- 
pli- 
cates. 

Av- 
er- 
ages. 

Du- 
pli- 
cates. 

Av- 
er- 
ages. 

1 

None 

9.3 
10.0 
11.3 
10.8 
5.9 
5.9 
5.9 

5.8 

'ii.'o' 

"'5*9' 
5.8 

12.3 
12.5 
12.5 
12.5 
6.1 
8.0 
7.0 

7.4 

"\2  A 
"\2.'b 
"7.6" 

7.2 

20.0 
20.0 
19.5 
20.0 
18.0 
18.0 
17.5 

18.0 

"26.6" 
"19.7" 

'is.' 6' 

17.7 

3.2 
3.2 
3.7 
3.5 
2.4 
2.7 
3.0 

2.5 

"3.Y 

"'3.'6" 

"h'.b 

2.7 

6.5 
6.0 
11.0 
9.8 
7.0 
6.8 
5.5 

7.5 

"6."2" 
'i6.'4' 
""6.Y 

6.5 

5.0 
4.7 
2.2 
2.9 
1.0 
1.4 
1.4 

1.2 

2 

3 

4 

5. 

6 

7 

8 

do 

2gm.  CaCOs 

do 

2gm.  MgC03 

do 

2  gm.  CaC03  +  2 

gm.  MgCOs. 
do 

4.8 

""*2."5 

'i.2 

1.3 

SOY  BEAN  CAKE  MEAL,  2  GRAMS. 


None.. 
do. 


2  gm.  CaC03. 
do 


2  gm.  MgC03 
do 


2  gm.  CaCOs  - 

gm.  MgC03. 

do 


18.5 
15.0 
14.5 
15.0 
16.5 
20.0 
14.0 

22.0 


16.7 
14.' 7 


18.2 


18.0 


15.0 
17.5 
19.0 
20.0 


10.5 


16.2 
19.5 


9.3 


13.2 


21.5 
22.0 
22.0 
20.0 
19.0 
19.5 
19.5 

19.5 


21.7 
2i."6" 

19.' 2' 

19.5 


4.5 
4.6 
5.0 
5.5 
5.4 
3.5 
3.0 

2.5 


4.5 
'5.2' 
'4.'4' 

2.7 


16.0 
14.0 
23.5 
21.0 
18.0 
20.0 
13.5 

16.5 


15.0 
22.'  2 
i9.'6' 

15.0 


45.0 
45.0 
68.0 
66.0 
4.0 
3.9 
4.3 

4.3 


45.0 
'67.0 


4.3 


AMMONIUM  SULPHATE.  1.2  GRAMS. 


None.. 
do. 


2  gm.  CaCOs 

do 

2  gm.  MgCOs 

do 

2  gm.  CaCOs  +  2 

gm.  MgC03. 
do 


2.0 
2.2 
3.8 
5.5 
.5 
.5 


2.1 


4.0 
4.1 
9.0 
9.2 
3.2 
3.0 
3.1 

3.3 


4.0 
9."i 

3.2 


17.0 
16.8 
16.0 
15.0 
17.0 
16.5 
16.5 

17.0 


16.9 
15.5 


16.7 


16.7 


1.4 
1.5 
1.7 
1.5 
1.4 
1.4 
1.9 

1.8 


1.4 

i'4" 


3.5 
3.3 
3.6 
3.9 
3.1 
3.1 
3.0 

3.0 


3.4 
"3.7 
"z'.'i 

3.0 


4.6 
5.0 
8.3 
7.3 
1.7 
1.9 
2.1 

2.0 


4.8 

'7.' 8 

"i.*8 

2.0 


From  these  data  it  is  shown  that  the  nitrification  of  dried  blood 
was  stimulated  by  calcium  carbonate  in  soils  Nos.  292  and  448, 
while  no  effects  were  produced  in  soils  Nos.  288,  329,  and  428; 
magnesium  carbonate,  on  the  other  hand,  proved  toxic  in  Nos.  292, 
288,  428,  and  485,  while  in  soils  Nos.  329  and  448  it  was  without 
effect. 

In  the  nitrification  of  soy  bean  cake  meal  we  find  that  calcium 
carbonate  produced  but  little  effect  in  soils  Nos.  292,  329,  and  428? 
but  was  stimulating  in  soils  Nos.  288,  448,  and  485;  the  addition  of 
magnesium  carbonate  produced  stimulation  in  soil  Nos.  292  and  448, 
was  without  effect  in  No.  428,  while  in  soils  Nos.  288  and  485,  par- 
ticularly the  latter,  notably  toxic  effects  were  produced. 

In  the  nitrification  of  ammonium  sulphate,  results  somewhat 
different  were  found.  Calcium  carbonate  caused  considerable 
stimulation  in  soils  Nos.  292,  288,  and  485,  while  in  Nos.  329,  428, 
and  448  it  was  without  effect.     Magnesium  carbonates,  on  the  other 


45 

hand,  proved  toxic  in  soils  Nos.   292,   288,  and  485,   and  exerted 
practically  no  effects  in  each  of  the  other  soils. 

In  general,  the  simultaneous  addition  of  calcium  and  magnesium 
carbonates  produced  effects  similar  to  those  produced  by  magnesium 
carbonates  alone.  In  the  soils  and  with  the  nitrogenous  materials 
with  which  calcium  carbonate  proved  most  stimulating,  magnesium 
carbonate  was  most  markedly  toxic.  Soy  bean  cake  meal  was  on  the 
whole  more  readily  nitrified  than  dried  blood  or  ammonium  sulphate 
notwithstanding  the  fact  that  only  165  milligrams  of  nitrogen  was 
added  in  the  soy  bean  cake  meal,  while  265  milligrams  was  added 
in  dried  blood  and  240  milligrams  in  the  ammonium  sulphate.  Neither 
is  this  fact  to  be  attributed  to  the  lack  of  ammonification  in  the  case  of 
dried  blood,  for  by  referring  to  previous  ammonification  experiments 
it  will  be  seen  that  vigorous  ammonification  of  dried  blood  took  place 
in  these  soils,  and  furthermore,  the  amount  of  ammonia  formed 
in  each  instance  was  greatly  in  excess  of  the  nitrate.  It  is  possible 
that  too  great  concentration  of  ammonium  sulphate  was  used  for  the 
best  action  of  the  nitrifiers.  On  the  whole  the  nitrifying  power 
of  these  soils  is  rather  low,  especially  in  the  case  of  ammonium 
sulphate. 

NITRIFICATION  IN  MANGANIFEROTJS    SOILS. 

There  are  considerable  areas  of  highly  manganiferous  soils  on 
Oabu  on  which  pineapples  make  very  poor  growth.  In  order  to 
throw  some  light  on  nitrification  in  these  soils,  a  series  of  experiments 
was  carried  out,  using  both  calcium  and  magnesium  carbonates. 
The  results  are  shown  in  the  following  table: 

Effects  of  calcium  and  magnesium  carbonates  on  nitrification  in  manganese  soils. 

[Average  amount  in  milligrams  of  nitrate  nitrogen  per  100  grams  soil.] 

DRIED  BLOOD,  2  GRAMS. 


son 

por- 
tions. 

Carbonate  added. 

Son 
No. 

514. 

son    i 

No. 
515.      j 

Son 

por- 
tions. 

Carbonate  added. 

Son 
No. 
514. 

Son 
No. 
515. 

1,2 

None 

28.0 

37.0 

3.5 

6.5 

7.8 

2  gm.    CaC03  +  2    gm. 
MgC03 

4.2 

3,4 

2gm.  CaC03 

5.2 
1.1  1 

1  1 

5,6 

2  gm.  MgC03 

SOY  BEAN  CAKE  MEAL,  2  GRAMS. 


9,10.... 
11,12... 
13,14... 


None 

2gm.  CaC03. 
2gm.MgC03. 


61.0 

26.4 

15,16... 

94.0 

11.4 

15.2 

4.1 

2   jmi.    CaC03  +  2   gm. 
MgC03 


13.5 


4.1 


AMMONIUM  SULPHATE,  1.2  GRAMS. 


17,18... 
19,20... 
21,22... 


None 

2gm.  CaC03. 
2  gm.  MgC03. 


7.8 

3.5 

23,24... 

6.1 

1.7 

2.5 

1.1 

2   gm.    CaC03  +  2   gm. 
MgC03 


2.4 


46 

The  above  data  show  that  nitrification  takes  place  in  the  manganif- 
erous  1  soils  quite  as  vigorously  as  in  other  island  soils.  The  addition 
of  calcium  carbonate  caused  stimulation  in  the  nitrification  of  dried 
blood  and  soy  bean  cake  meal  in  soil  No.  514,  while  in  soil  No.  515  it 
caused  a  reduction  in  the  nitrification  of  each  of  the  materials  used. 
In  each  instance  magnesium  carbonate  proved  markedly  toxic,  and 
the  addition  of  calcium  carbonate  did  not  overcome  the  toxic  effects. 

EFFECTS  OF  CALCAREOUS   AND  DOLOMITIC  LIMESTONES   ON 

NITRIFICATION. 

The  following  series  of  experiments  show  the  effects  produced  by 
pulverized  limestone  and  dolomitic  limestone  in  comparison  with 
chemically  pure  calcium  and  magnesium  carbonates. 

Effects  of  calcium  and  magnesium  carbonates  and  different  limestones  on  nitrification. 
[Average  amount  in  milligrams  of  nitrate  nitrogen  per  100  grams  soil.] 


Soil 
por- 
tions. 


1,2... 
3,4... 


Carbonate  added. 


None 

2gm.  CaC03 

2gm.  MgC03 

1.1  gm.  CaCO3+0.9  gm 
MgC03 


Soil 
No. 

485— 
Soy- 
bean 
cake. 


44.5 
67.0 
3.8 

8.2 


Soil 
No. 
516— 
Soy- 
bean 
cake. 


13.0 
9.0 
5.3 

6.4 


Soil 

No. 

292— 

Dried 

blood. 


11.8 

8.7 


J.  8 


Soil 
por- 
tions. 


9,10.. 
11,12. 


Carbonate  added. 


2  gm.  limestone  (CaC03) 
2  gm.  dolomite 


Soil 

Soil 

No. 

No. 

485— 

516— 

Soy- 

Soy- 

bean 

bean 

cake. 

cake. 

60.0 

10.0 

70.0 

13.1 

Soil 

No. 

292— 

Dried 

blood. 


Again  it  will  be  seen  that  calcium  carbonate  produced  notable 
stimulation  in  the  nitrification  of  soy  bean  cake  meal  in  soil  No.  485 
and  a  retardation  in  No.  516.  Magnesium  carbonate  again  proved 
toxic  in  each  instance,  and  the  simultaneous  addition  of  calcium  and 
magnesium  carbonates,  in  the  amounts  in  which  they  occur  in  dolo- 
mite, produced  effects  similar  to  those  of  magnesium  carbonate  alone. 
When  we  come  to  the  natural  limestones,  it  will  be  seen  that  both 
the  calcareous  and  dolomitic  limestones  produced  effects  very  similar 
to  those  produced  by  calcium  carbonate,  and  that  no  toxicity  was 
produced  in  any  case  by  the  dolomitic  limestone. 

DISCUSSION. 

From  the  experiments  above  recorded,  it  has  been  shown  that 
calcium  carbonate  produced  only  slight  stimulation  of  the  ammoni- 
fication  of  dried  blood  and  soy  bean  cake  meal  in  most  of  the  soils 
studied.  Magnesium  carbonate,  on  the  other  hand,  caused  consid- 
erable stimulation  in  the  ammonification  of  dried  blood  in  a  majority 
of  the  soils,  while  in  a  number  of  instances  the  effects  on  the  ammoni- 
fication of  soy  bean  cake  meal  were  negligible.     In  two  soils  only, 


i  See  Hawaii  Sta.  Bui.  26  (1912),  p.  55. 


47 

Nos.  335  and  461,  magnesium  carbonate  produced  toxic  effects,  and 
in  the  former  the  effects  on  the  ammonification  of  dried  blood  were 
quite  similar  to  those  found  from  the  use  of  the  sandy  soils  from  Cal- 
ifornia.1 But  the  smaller  amounts  of  ammonia,  that  accumulated 
in  the  presence  of  magnesium  carbonate,  were  not  entirely  due  to  the 
volatilization  of  ammonia.  Hence,  magnesium  carbonate  was  toxic 
to  some  extent.  No  antagonism  to  the  action  of  magnesium  car- 
bonate was  produced  by  calcium  carbonate,  but  since  magnesium 
carbonate  is  more  soluble  than  calcium  carbonate  we  are  not  justified 
in  affirming  that  no  significance  is  to  be  attached  to  the  lime-magnesia 
ratio.  It  seems  probable,  however,  that  the  stimulating  effects  pro- 
duced by  magnesium  carbonate,  on  the  one  hand,  and  the  toxic  effects 
on  the  other,  were  not  due  to  variations  in  this  ratio,  but  rather  to 
changes  in  the  concentration  of  magnesium  and  to  double  decompo- 
sitions. 

Magnesium  carbonate  stimulated  the  ammonification  of  dried 
blood  in  soils  which  already  contained  abnormally  high  amounts 
of  magnesium,  and,  since  ammonia  is  an  available  form  of  nitrogen, 
the  application  of  magnesium  carbonate  to  these  soils  might  prove 
of  practical  value  to  crops.  The  magnesium  in  these  soils  exists 
largely  as  hydrous  silicates,  and  though  present  in  much  greater 
amounts  than  calcium,  is  considerably  less  soluble  in  dilute  acids 
and  water,  and  consequently  is  probably  not  present  in  the  soil  solu- 
tions in  amounts  equal  to  those  of  calcium.  It  has  been  shown  in  a 
different  connection  that  Hawaiian  soils  have  a  remarkably  high 
absorptive  power  for  a  number  of  chemical  substances.  Potassium, 
for  instance,  is  fixed  in  relatively •  large  amounts,  but  at  the  same 
time  corresponding  amounts  of  calcium  and  magnesium  are  set  free. 

Now,  in  all  the  soils  studied  above,  save  No.  335,  it  is  probable 
that  a  soluble  salt  of  magnesium  (in  this  instance  magnesium  car- 
bonate and  the  salts  of  organic  acids  formed  through  the  reaction 
between  magnesium  carbonate  and  the  organic  acids  set  free  in  the 
decomposition  of  the  materials  added),  would  become  fixed  through 
double  decomposition,  thus  setting  free  potassium,  sodium,  and  cal- 
cium. Therefore,  the  concentration  of  the  several  constituents  in  the 
soil  moisture  would  become  greatly  changed  as  a  result  of  adding  mag- 
nesium carbonate.  Hence,  the  effects  produced  by  magnesium  car- 
bonate on  ammonification  are  probably  complex,  and  can  hardly  be 
attributed  wholly  to  its  acting  on  the  bacteria  directly.  The  fact 
that  magnesium  carbonate  caused  no  loss  of  ammonia  in  most  of  these 
soils  is  probably  due  to  their  fixing  power  for  ammonia,  which  has 
been  shown  elsewhere  to  be  unusually  high.  In  every  instance, 
except  one,  no  antagonism  to  the  effects  produced  by  magnesium 
carbonate,  either  stimulating  or  toxic,  resulted  from  the  addition  of 

•  Loc.  cit. 


48 

calcium  carbonate.  Therefore,  the  effects  on  ammonification  pro- 
duced by  magnesium  and  carbonates  present  a  striking  contrast,  and 
the  effects  produced  by  the  former  suggest  that  the  amounts  of  solu- 
ble magnesium  in  soils  exerts  an  important  bearing  on  bacterial 
action. 

While  magnesium  carbonate  produced  striking  effects  on  ammoni- 
fication, the  question  loses  much  of  its  practical  significance  for  the 
reason  that  magnesian  limestone  exerted  effects  similar  to  those 
brought  about  by  calcium  carbonate,  and  in  no  way  comparable  to 
those  produced  by  magnesium  carbonate. 

When  we  come  to  nitrification,  it  was  found  that  calcium  carbon- 
ate produced  stimulation  in  a  few  instances,  although  the  increases 
in  nitrate,  with  one  exception,  were  small.1  The  carbonate  content 
of  most  of  these  soils  is  low,  usually  less  than  0.1  per  cent.  Generally 
calcium  carbonate  has  been  found  to  stimulate  nitrification  in  soils 
which  contain  such  low  amounts  of  carbonate.  That  such  is  not 
the  case  in  Hawaiian  soils  is  probably  due  to  the  large  amounts  of 
aluminum  and  ferric  hydrates  present,  which  substances  take  the 
place  of  calcium  carbonate  in  maintaining  the  neutral  conditions 
as  shown  by  Ashby.2 

In  the  case  of  magnesium  carbonate,  it  was  found  that  nitrification 
was  hindered  in  soils  Nos.  485,  514,  and  515.  The  toxic  effects 
were  striking,  but  as  in  the  case  of  ammonification,  practically  no 
antagonism  was  found  between  calcium  and  magnesium  carbonates. 
Dolomitic  limestone,  however,  produced  effects  very  similar  to  cal- 
cium carbonate,  causing  stimulation  in  the  soils  in  which  calcium 
carbonate  produced  stimulation,  and  no  effects  in  the  soils  that  were 
unaffected  by  calcium  carbonate. 

It  is  not  possible  to  explain  fully  the  action  of  magnesium  carbonate. 
It  seems  probable,  however,  that  the  nitrifying  floras  of  different  soils 
would  be  affected  differently  by  magnesium  carbonate,  being  toxic 
in  some  soils  and  without  effect  in  others.  It  will  be  observed  by 
reference  to  the  table  (p.  45)  that  the  effects  produced  in  certain  soils 
by  magnesium  carbonate  depended  on  the  nitrogenous  material  being 
acted  upon.  This  may  be  accounted  for,  in  part,  by  the  dried  blood 
and  soy  bean  cake  meal  having  reacted  unequally  on  the  growth  of 
those  organisms  which  feed  upon  ammonia  and  nitrates.  It  was 
observed,  for  instance,  that  wherever  magnesium  carbonate  was 
added  a  more  abundant  growth  of  molds  took  place.  The  organic 
acids  formed  in  the  decay  of  the  materials  must  have  reacted  with 
the  magnesium  carbonate,  leading  to  the  formation  of  different 
organic  salts,   the  specific  effects  of  which  are  nojb  known.     It  is 

*"  Peck  has  shown  that  calcium  carbonate  produces  considerable  stimulation  on  nitrification  in  some  of 
the  sugar  lands  of  the  islands.    See  Hawaiian  Sugar  Planters3  Sta.,  Agr.  and  Chem.  Bui.  37  (1911). 
2  Loc.  cit. 


43 

probable,  however,  that  compounds  of  unequal  solubility  and  of 
different  action  on  the  nitrifying  bacteria  were  formed.  If  so,  the 
differences  observed  in  the  nitrification  of  dried  blood  and  soy-bean 
cake  in  one  and  the  same  soil  were  probably  due,  in  part  at  least,  to 
causes  of  this  nature,  since  the  nonnitrogenous  constituents  of  these 
materials  differ  greatly.  The  dried  blood  contained  a  very  small 
nitrogen-free  extract,  while  the  soy  bean  cake  meal  contained  more 
than  30  per  cent. 

That  dolomite  produced  effects  unlike  those  of  magnesium  car- 
bonate is  probably  due  to  the  insoluble  nature  of  this  material,  and 
also  to  the  fact  that  dolomite  reacts  with  acids  of  various  sorts  less 
energetically  even  than  calcium  carbonate.  Consequently  the  mag- 
nesium contained  in  the  dolomite  probably  remained  insoluble  during 
the  time  of  the  experiments. 

In  the  first  series  of  experiments  on  ammonification  (p.  39) 
Baker's  analyzed  magnesium  carbonate,  having  the  composition 
3MgC03.Mg(OH2)3H20,  was  used.  As  already  pointed  out,  consid- 
erable stimulation  was  produced  by  this  material  in  two  heavy  clay 
soils,  which  stimulation  was  slightly  greater  than  that  produced  by 
corresponding  amounts  of  calcium  carbonate,  while  the  effects  in  a 
sandy  soil  were  pronouncedly  toxic.  It  was  suggested  that  these 
results  were  in  part  referable  to  the  magnesium  hydrate  contained 
in  this  material.  With  the  hope  of  eliminating  magnesium  hydrate 
from  consideration,  Merck's  reagent  magnesium  carbonate,  which  is 
claimed  to  be  free  from  the  hydrate,  was  used  in  all  the  subsequent 
experiments.  This  material,  however,  probably  also  contained  some 
magnesium  hydrate,  as  a  saturated  solution  of  it  proved  to  be  of 
approximately  the  same  alkalinity  to  methyl  orange  as  a  saturated 
solution  of  Baker's  carbonate.  It  is  not  certain,  however,  that  the 
stimulation  given  to  ammonification,  as  compared  with  that  of  cal- 
cium carbonate,  or  the  toxicity  found  in  certain  instances,  was  due  to 
alkalinity. 

In  the  experiments  previously  reported  by  the  writer  using  sandy 
soils  from  California,1  Baker's  magnesium  carbonate  was  used,  and 
marked  toxicity,  both  to  ammonification  and  nitrification,  was  pro- 
duced. It  was  found,  for  instance,  that  the  addition  of  0.1  per  cent 
magnesium  carbonate  proved  toxic  to  a  considerable  degree  and 
that  0.4  per  cent  produced  practically  maximum  toxicity.  Subse- 
quently it  has  been  found  that  the  alkalinity  of  water  extracts 
obtained  by  leaching  portions  of  one  of  these  soils  after  ammonifica- 
tion had  ensued  for  seven  days,  bore  no  relation  to  the  toxic  or 
stimulating  effects  produced  by  magnesium  or  calcium  carbonates, 
respectively.     On  the  other  hand,  C.  B.  Lipman  2  has  shown  from 

1  Loc.  eft. 

-Centbl.  Bakt.  [etc.],  2.  Abt.,  32  (1911),  pp.  58-64. 


90 

experiments  with  a  similar  sandy  soil  from  California  that  consider- 
able stimulation  to  ammonification  was  produced  by  the  addition  of 
0.4  per  cent  sodium  carbonate,  a  compound  generally  considered  to 
be  strongly  alkaline.  It  seems  probable,  therefore,  that  the  alkalin- 
ity of  the  magnesium  carbonate  was  not  responsible  for  the  toxic 
effects  in  the  California  soils. 

The  difficulties  inherent  in  the  determination  of  actual  acidity  in 
soils  are  very  great.  Hawaiian  soils,  as  stated  above,  generally  have 
a  high  absorptive  power  for  soluble  bases,  and  the  adsorptive  effects 
and  other  physical  phenomena  that  are  produced  when  a  soluble  salt 
is  added  to  a  soil  must  be  considered.  In  view  of  all  these  facts  it  is 
difficult  to  determine  whether  the  greater  alkalinity  of  the  magnesium 
carbonate  was  a  factor  to  be  considered  in  the  above  experiments. 
It  is  true,  however,  that  Hawaiian  soils  are  potentially  basic  and 
hence  it  seems  improbable  that  magnesium  carbonate  would  cause 
greater  stimulation  to  bacterial  action  than  calcium  carbonate  on 
account  of  its  being  more  actively  alkaline,  especially  when  the  latter 
was  added  in  amounts  equal  to  2  per  cent  of  the  soil.  It  is  possible 
that  excessive  alkalinity  had  something  to  do  with  the  marked 
toxicity  to  nitrification  noted  in  certain  instances. 

SUMMARY. 

(1)  The  pasture  and  forest  lands  of  Hawaii,  the  soils  used  for 
aquatic  crops,  and  most  other  island  soils  not  subjected  to  frequent 
tillage  contain  very  small  amounts  of  nitrate  but  considerably 
larger  amounts  of  ammonia. 

(2)  The  uncultivated  soils  are  capable  of  supporting  vigorous 
ammonification  of  dried  blood,  but  are  toxic  to  nitrification. 

(3)  Nitrification  takes  place  in  Hawaiian  soils  after  aerated 
conditions  have  been  maintained  for  a  period  of  several  months,  but 
not  immediately  following  tillage.  Ammonification  is  also  stimu- 
lated by  tillage. 

(4)  The  inactive  state  of  nitrification  in  the  uncultivated  soils 
is  not  due  to  the  absence  of  the  nitrifying  organisms  or  acidity. 

(5)  Sterilization  in  the  autoclave  and  burning  failed  to  bring  about 
conditions  favorable  to  nitrification,  but  burning  caused  a  splitting 
off  of  large  amounts  of  ammonia. 

(6)  The  beneficial  effects  to  crops  produced  by  burning  refuse 
is  probably  due  in  considerable  part  to  the  formation  of  ammonia. 

(7)  The  plants  growing  on  the  uncultivated  soils  probably  absorb 
nitrogen  largely  in  the  form  of  ammonium  compounds. 

(8)  Partial  sterilization  of  Hawaiian  soils  stimulates  ammonifi- 
cation for  a  short  time,  usually  about  two  weeks,  followed  then  by 
a  retardation   in    ammonification.     Nitrification   is  inhibited    tern- 


51 

porarily  by  partial  sterilization,  but  later  on  regains  its  activity, 
due  possibly  to  reinoculation  with  air-borne  organisms. 

(9)  Reinoculation  of  the  partially  sterilized  with  untreated  soil 
did  not  overcome  the  stimulation  to  ammonification,  but  stimulated 
nitrification. 

(10)  A  permanent  increase  in  the  available  nitrogen  (nitrate  and 
ammonia)  was  effected  by  partial  sterilization  in  certain  soils,  while 
in  others  the  effects  were  very  temporary.  In  the  latter  instances 
it  is  possible  that  nitrate  and  ammonia  consuming  organisms  gained 
the  ascendancy  toward  the  close  of  the  experimental  periods,  and 
that  ammonification  was  partially  inhibited  by  the  too  great  accu- 
mulation of  the  products  of  bacterial  action. 

(11)  Two-tenths  per  cent  of  toluol  and  carbon  bisulphid  were 
equally  as  effective  as  4  per  cent. 

(12)  It  is  believed  that  both  the  aeration  and  partial  sterilization 
of  Hawaiian  soils  bring  about  stimulation  in  bacterial  action  through 
effects  produced  on  the  colloidal  soil  films,  but  continued  aeration 
is  the  more  effective.  The  protozoan  theory  appears  to  be  of  doubtful 
application  to  these  soils. 

(13)  Calcium  carbonate  produced  considerable  stimulation  in  the 
ammonification  of  dried  blood  and  soy  bean  cake  meal  in  certain 
soils;  in  others,  only  slight  effects.  Magnesium  carbonate,  on  the 
other  hand,  produced  marked  stimulation  in  a  number  of  instances. 
In  two  soils  only,  magnesium  carbonate  was  toxic  to  ammonifica- 
tion. Dolomitic  and  calcareous  limestones  produced  effects  similar 
to  those  produced  by  calcium  carbonate. 

(14)  In  certain  soils  calcium  carbonate  stimulated  nitrification, 
while  in  others  no  effects  were  produced.  Magnesium  carbonate, 
on  the  other  hand,  was  toxic  to  nitrification  in  a  majority  of  the 
soils  studied. 

(15)  Nitrification  was  found  to  be  equally  as  active  in  the  man- 
ganiferous  and  titaniferous  soils  as  in  the  other  soils  studied,  but 
magnesium  carbonate  was  especially  toxic  in  these  soils,  and  was 
more  toxic  to  the  nitrification  of  soy  bean  cake  meal  than  of  dried 
blood. 

(16)  Dolomitic  and  calcareous  limestones  produced  similar  effects 
on  nitrification,  bringing  about  stimulation  in  the  soils  in  which 
calcium  carbonate  produced  stimulation  and  no  effects  in  the  soils 
that  were  unaffected  by  calcium  carbonate. 

(17)  The  application  of  calcareous  and  dolomitic  limestones  will 
probably  produce  similar  effects  on  the  availability  of  nitrogen 
in  Hawaiian  soils,  but  regarding  the  effects  of  the  burnt  limes,  further 
experiments  are  necessary  before  conclusions  can  be  drawn. 

(18)  Positive  conclusion  can  not  be  drawn  concerning  the  effects  of 
the  lime-magnesia  ratio  on  ammonification  and  nitrification  in  soils. 


52 

The  evidence  to  date,  however,  points  to  the  probability  that  this 
ratio  exerts  very  little,  if  any,  influence  on  bacterial  action  in  the 
usual  soil.  The  concentration  of  magnesium  salts  in  the  soil  moisture, 
on  the  other  hand,  probably  has  an  important  influence  on  bacterial 
action. 

(19)  The  experiments  recorded  in  this  bulletin  emphasize  the 
importance  of  maintaining  the  best  aeration  possible.  This  can 
not  be  done  profitably  without  the  rotation  of  crops,  including 
green  manuring.  The  exceedingly  high  clay  content  of  much  of 
the  cultivated  lands  causes  the  soil  to  be  very  heavy,  and  to  pack 
after  rains,  so  that  aeration  becomes  poor.  By  increasing  the  humus 
content  aeration  will  be  increased,  drainage  facilitated,  and  bacterial 
action  stimulated.  Thus,  the  plant  food  will  become  more  available, 
deeper  rooting  of  crops  be  encouraged,  and  their  ability  to  withstand 
the  effects  of  drought  be  greatly  increased.  No  system  of  soil 
management  in  Hawaii  can  be  judicious  or  permanent  without  the 
rotation  of  crops  and  the  maintenance  of  humus. 


ADDITIONAL  COPIES 

OF  THIS  PUBLICATION  MAY  BE  PROCURED  FROM 

THE  SUPERINTENDENT  OF  DOCUMENTS 

GOVERNMENT  PRINTING  OFFICE 

■WASHINGTON,  D.   C. 

AT 

10  CENTS  PER  COPY 


UNIVERSITY  OF  FLORIDA 

IIIIIIIII. 

3  1262  08929  1024 


